The Definitive KVM (Kernel-based Virtual Machine) API Documentation =================================================================== 1. General description ---------------------- The kvm API is a set of ioctls that are issued to control various aspects of a virtual machine. The ioctls belong to three classes - System ioctls: These query and set global attributes which affect the whole kvm subsystem. In addition a system ioctl is used to create virtual machines - VM ioctls: These query and set attributes that affect an entire virtual machine, for example memory layout. In addition a VM ioctl is used to create virtual cpus (vcpus). Only run VM ioctls from the same process (address space) that was used to create the VM. - vcpu ioctls: These query and set attributes that control the operation of a single virtual cpu. Only run vcpu ioctls from the same thread that was used to create the vcpu. 2. File descriptors ------------------- The kvm API is centered around file descriptors. An initial open("/dev/kvm") obtains a handle to the kvm subsystem; this handle can be used to issue system ioctls. A KVM_CREATE_VM ioctl on this handle will create a VM file descriptor which can be used to issue VM ioctls. A KVM_CREATE_VCPU ioctl on a VM fd will create a virtual cpu and return a file descriptor pointing to it. Finally, ioctls on a vcpu fd can be used to control the vcpu, including the important task of actually running guest code. In general file descriptors can be migrated among processes by means of fork() and the SCM_RIGHTS facility of unix domain socket. These kinds of tricks are explicitly not supported by kvm. While they will not cause harm to the host, their actual behavior is not guaranteed by the API. The only supported use is one virtual machine per process, and one vcpu per thread. 3. Extensions ------------- As of Linux 2.6.22, the KVM ABI has been stabilized: no backward incompatible change are allowed. However, there is an extension facility that allows backward-compatible extensions to the API to be queried and used. The extension mechanism is not based on the Linux version number. Instead, kvm defines extension identifiers and a facility to query whether a particular extension identifier is available. If it is, a set of ioctls is available for application use. 4. API description ------------------ This section describes ioctls that can be used to control kvm guests. For each ioctl, the following information is provided along with a description: Capability: which KVM extension provides this ioctl. Can be 'basic', which means that is will be provided by any kernel that supports API version 12 (see section 4.1), a KVM_CAP_xyz constant, which means availability needs to be checked with KVM_CHECK_EXTENSION (see section 4.4), or 'none' which means that while not all kernels support this ioctl, there's no capability bit to check its availability: for kernels that don't support the ioctl, the ioctl returns -ENOTTY. Architectures: which instruction set architectures provide this ioctl. x86 includes both i386 and x86_64. Type: system, vm, or vcpu. Parameters: what parameters are accepted by the ioctl. Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL) are not detailed, but errors with specific meanings are. 4.1 KVM_GET_API_VERSION Capability: basic Architectures: all Type: system ioctl Parameters: none Returns: the constant KVM_API_VERSION (=12) This identifies the API version as the stable kvm API. It is not expected that this number will change. However, Linux 2.6.20 and 2.6.21 report earlier versions; these are not documented and not supported. Applications should refuse to run if KVM_GET_API_VERSION returns a value other than 12. If this check passes, all ioctls described as 'basic' will be available. 4.2 KVM_CREATE_VM Capability: basic Architectures: all Type: system ioctl Parameters: machine type identifier (KVM_VM_*) Returns: a VM fd that can be used to control the new virtual machine. The new VM has no virtual cpus and no memory. You probably want to use 0 as machine type. In order to create user controlled virtual machines on S390, check KVM_CAP_S390_UCONTROL and use the flag KVM_VM_S390_UCONTROL as privileged user (CAP_SYS_ADMIN). To use hardware assisted virtualization on MIPS (VZ ASE) rather than the default trap & emulate implementation (which changes the virtual memory layout to fit in user mode), check KVM_CAP_MIPS_VZ and use the flag KVM_VM_MIPS_VZ. 4.3 KVM_GET_MSR_INDEX_LIST Capability: basic Architectures: x86 Type: system Parameters: struct kvm_msr_list (in/out) Returns: 0 on success; -1 on error Errors: E2BIG: the msr index list is to be to fit in the array specified by the user. struct kvm_msr_list { __u32 nmsrs; /* number of msrs in entries */ __u32 indices[0]; }; This ioctl returns the guest msrs that are supported. The list varies by kvm version and host processor, but does not change otherwise. The user fills in the size of the indices array in nmsrs, and in return kvm adjusts nmsrs to reflect the actual number of msrs and fills in the indices array with their numbers. Note: if kvm indicates supports MCE (KVM_CAP_MCE), then the MCE bank MSRs are not returned in the MSR list, as different vcpus can have a different number of banks, as set via the KVM_X86_SETUP_MCE ioctl. 4.4 KVM_CHECK_EXTENSION Capability: basic, KVM_CAP_CHECK_EXTENSION_VM for vm ioctl Architectures: all Type: system ioctl, vm ioctl Parameters: extension identifier (KVM_CAP_*) Returns: 0 if unsupported; 1 (or some other positive integer) if supported The API allows the application to query about extensions to the core kvm API. Userspace passes an extension identifier (an integer) and receives an integer that describes the extension availability. Generally 0 means no and 1 means yes, but some extensions may report additional information in the integer return value. Based on their initialization different VMs may have different capabilities. It is thus encouraged to use the vm ioctl to query for capabilities (available with KVM_CAP_CHECK_EXTENSION_VM on the vm fd) 4.5 KVM_GET_VCPU_MMAP_SIZE Capability: basic Architectures: all Type: system ioctl Parameters: none Returns: size of vcpu mmap area, in bytes The KVM_RUN ioctl (cf.) communicates with userspace via a shared memory region. This ioctl returns the size of that region. See the KVM_RUN documentation for details. 4.6 KVM_SET_MEMORY_REGION Capability: basic Architectures: all Type: vm ioctl Parameters: struct kvm_memory_region (in) Returns: 0 on success, -1 on error This ioctl is obsolete and has been removed. 4.7 KVM_CREATE_VCPU Capability: basic Architectures: all Type: vm ioctl Parameters: vcpu id (apic id on x86) Returns: vcpu fd on success, -1 on error This API adds a vcpu to a virtual machine. No more than max_vcpus may be added. The vcpu id is an integer in the range [0, max_vcpu_id). The recommended max_vcpus value can be retrieved using the KVM_CAP_NR_VCPUS of the KVM_CHECK_EXTENSION ioctl() at run-time. The maximum possible value for max_vcpus can be retrieved using the KVM_CAP_MAX_VCPUS of the KVM_CHECK_EXTENSION ioctl() at run-time. If the KVM_CAP_NR_VCPUS does not exist, you should assume that max_vcpus is 4 cpus max. If the KVM_CAP_MAX_VCPUS does not exist, you should assume that max_vcpus is same as the value returned from KVM_CAP_NR_VCPUS. The maximum possible value for max_vcpu_id can be retrieved using the KVM_CAP_MAX_VCPU_ID of the KVM_CHECK_EXTENSION ioctl() at run-time. If the KVM_CAP_MAX_VCPU_ID does not exist, you should assume that max_vcpu_id is the same as the value returned from KVM_CAP_MAX_VCPUS. On powerpc using book3s_hv mode, the vcpus are mapped onto virtual threads in one or more virtual CPU cores. (This is because the hardware requires all the hardware threads in a CPU core to be in the same partition.) The KVM_CAP_PPC_SMT capability indicates the number of vcpus per virtual core (vcore). The vcore id is obtained by dividing the vcpu id by the number of vcpus per vcore. The vcpus in a given vcore will always be in the same physical core as each other (though that might be a different physical core from time to time). Userspace can control the threading (SMT) mode of the guest by its allocation of vcpu ids. For example, if userspace wants single-threaded guest vcpus, it should make all vcpu ids be a multiple of the number of vcpus per vcore. For virtual cpus that have been created with S390 user controlled virtual machines, the resulting vcpu fd can be memory mapped at page offset KVM_S390_SIE_PAGE_OFFSET in order to obtain a memory map of the virtual cpu's hardware control block. 4.8 KVM_GET_DIRTY_LOG (vm ioctl) Capability: basic Architectures: x86 Type: vm ioctl Parameters: struct kvm_dirty_log (in/out) Returns: 0 on success, -1 on error /* for KVM_GET_DIRTY_LOG */ struct kvm_dirty_log { __u32 slot; __u32 padding; union { void __user *dirty_bitmap; /* one bit per page */ __u64 padding; }; }; Given a memory slot, return a bitmap containing any pages dirtied since the last call to this ioctl. Bit 0 is the first page in the memory slot. Ensure the entire structure is cleared to avoid padding issues. If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 specifies the address space for which you want to return the dirty bitmap. They must be less than the value that KVM_CHECK_EXTENSION returns for the KVM_CAP_MULTI_ADDRESS_SPACE capability. 4.9 KVM_SET_MEMORY_ALIAS Capability: basic Architectures: x86 Type: vm ioctl Parameters: struct kvm_memory_alias (in) Returns: 0 (success), -1 (error) This ioctl is obsolete and has been removed. 4.10 KVM_RUN Capability: basic Architectures: all Type: vcpu ioctl Parameters: none Returns: 0 on success, -1 on error Errors: EINTR: an unmasked signal is pending This ioctl is used to run a guest virtual cpu. While there are no explicit parameters, there is an implicit parameter block that can be obtained by mmap()ing the vcpu fd at offset 0, with the size given by KVM_GET_VCPU_MMAP_SIZE. The parameter block is formatted as a 'struct kvm_run' (see below). 4.11 KVM_GET_REGS Capability: basic Architectures: all except ARM, arm64 Type: vcpu ioctl Parameters: struct kvm_regs (out) Returns: 0 on success, -1 on error Reads the general purpose registers from the vcpu. /* x86 */ struct kvm_regs { /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */ __u64 rax, rbx, rcx, rdx; __u64 rsi, rdi, rsp, rbp; __u64 r8, r9, r10, r11; __u64 r12, r13, r14, r15; __u64 rip, rflags; }; /* mips */ struct kvm_regs { /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */ __u64 gpr[32]; __u64 hi; __u64 lo; __u64 pc; }; 4.12 KVM_SET_REGS Capability: basic Architectures: all except ARM, arm64 Type: vcpu ioctl Parameters: struct kvm_regs (in) Returns: 0 on success, -1 on error Writes the general purpose registers into the vcpu. See KVM_GET_REGS for the data structure. 4.13 KVM_GET_SREGS Capability: basic Architectures: x86, ppc Type: vcpu ioctl Parameters: struct kvm_sregs (out) Returns: 0 on success, -1 on error Reads special registers from the vcpu. /* x86 */ struct kvm_sregs { struct kvm_segment cs, ds, es, fs, gs, ss; struct kvm_segment tr, ldt; struct kvm_dtable gdt, idt; __u64 cr0, cr2, cr3, cr4, cr8; __u64 efer; __u64 apic_base; __u64 interrupt_bitmap[(KVM_NR_INTERRUPTS + 63) / 64]; }; /* ppc -- see arch/powerpc/include/uapi/asm/kvm.h */ interrupt_bitmap is a bitmap of pending external interrupts. At most one bit may be set. This interrupt has been acknowledged by the APIC but not yet injected into the cpu core. 4.14 KVM_SET_SREGS Capability: basic Architectures: x86, ppc Type: vcpu ioctl Parameters: struct kvm_sregs (in) Returns: 0 on success, -1 on error Writes special registers into the vcpu. See KVM_GET_SREGS for the data structures. 4.15 KVM_TRANSLATE Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_translation (in/out) Returns: 0 on success, -1 on error Translates a virtual address according to the vcpu's current address translation mode. struct kvm_translation { /* in */ __u64 linear_address; /* out */ __u64 physical_address; __u8 valid; __u8 writeable; __u8 usermode; __u8 pad[5]; }; 4.16 KVM_INTERRUPT Capability: basic Architectures: x86, ppc, mips Type: vcpu ioctl Parameters: struct kvm_interrupt (in) Returns: 0 on success, negative on failure. Queues a hardware interrupt vector to be injected. /* for KVM_INTERRUPT */ struct kvm_interrupt { /* in */ __u32 irq; }; X86: Returns: 0 on success, -EEXIST if an interrupt is already enqueued -EINVAL the the irq number is invalid -ENXIO if the PIC is in the kernel -EFAULT if the pointer is invalid Note 'irq' is an interrupt vector, not an interrupt pin or line. This ioctl is useful if the in-kernel PIC is not used. PPC: Queues an external interrupt to be injected. This ioctl is overleaded with 3 different irq values: a) KVM_INTERRUPT_SET This injects an edge type external interrupt into the guest once it's ready to receive interrupts. When injected, the interrupt is done. b) KVM_INTERRUPT_UNSET This unsets any pending interrupt. Only available with KVM_CAP_PPC_UNSET_IRQ. c) KVM_INTERRUPT_SET_LEVEL This injects a level type external interrupt into the guest context. The interrupt stays pending until a specific ioctl with KVM_INTERRUPT_UNSET is triggered. Only available with KVM_CAP_PPC_IRQ_LEVEL. Note that any value for 'irq' other than the ones stated above is invalid and incurs unexpected behavior. MIPS: Queues an external interrupt to be injected into the virtual CPU. A negative interrupt number dequeues the interrupt. 4.17 KVM_DEBUG_GUEST Capability: basic Architectures: none Type: vcpu ioctl Parameters: none) Returns: -1 on error Support for this has been removed. Use KVM_SET_GUEST_DEBUG instead. 4.18 KVM_GET_MSRS Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_msrs (in/out) Returns: 0 on success, -1 on error Reads model-specific registers from the vcpu. Supported msr indices can be obtained using KVM_GET_MSR_INDEX_LIST. struct kvm_msrs { __u32 nmsrs; /* number of msrs in entries */ __u32 pad; struct kvm_msr_entry entries[0]; }; struct kvm_msr_entry { __u32 index; __u32 reserved; __u64 data; }; Application code should set the 'nmsrs' member (which indicates the size of the entries array) and the 'index' member of each array entry. kvm will fill in the 'data' member. 4.19 KVM_SET_MSRS Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_msrs (in) Returns: 0 on success, -1 on error Writes model-specific registers to the vcpu. See KVM_GET_MSRS for the data structures. Application code should set the 'nmsrs' member (which indicates the size of the entries array), and the 'index' and 'data' members of each array entry. 4.20 KVM_SET_CPUID Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_cpuid (in) Returns: 0 on success, -1 on error Defines the vcpu responses to the cpuid instruction. Applications should use the KVM_SET_CPUID2 ioctl if available. struct kvm_cpuid_entry { __u32 function; __u32 eax; __u32 ebx; __u32 ecx; __u32 edx; __u32 padding; }; /* for KVM_SET_CPUID */ struct kvm_cpuid { __u32 nent; __u32 padding; struct kvm_cpuid_entry entries[0]; }; 4.21 KVM_SET_SIGNAL_MASK Capability: basic Architectures: all Type: vcpu ioctl Parameters: struct kvm_signal_mask (in) Returns: 0 on success, -1 on error Defines which signals are blocked during execution of KVM_RUN. This signal mask temporarily overrides the threads signal mask. Any unblocked signal received (except SIGKILL and SIGSTOP, which retain their traditional behaviour) will cause KVM_RUN to return with -EINTR. Note the signal will only be delivered if not blocked by the original signal mask. /* for KVM_SET_SIGNAL_MASK */ struct kvm_signal_mask { __u32 len; __u8 sigset[0]; }; 4.22 KVM_GET_FPU Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_fpu (out) Returns: 0 on success, -1 on error Reads the floating point state from the vcpu. /* for KVM_GET_FPU and KVM_SET_FPU */ struct kvm_fpu { __u8 fpr[8][16]; __u16 fcw; __u16 fsw; __u8 ftwx; /* in fxsave format */ __u8 pad1; __u16 last_opcode; __u64 last_ip; __u64 last_dp; __u8 xmm[16][16]; __u32 mxcsr; __u32 pad2; }; 4.23 KVM_SET_FPU Capability: basic Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_fpu (in) Returns: 0 on success, -1 on error Writes the floating point state to the vcpu. /* for KVM_GET_FPU and KVM_SET_FPU */ struct kvm_fpu { __u8 fpr[8][16]; __u16 fcw; __u16 fsw; __u8 ftwx; /* in fxsave format */ __u8 pad1; __u16 last_opcode; __u64 last_ip; __u64 last_dp; __u8 xmm[16][16]; __u32 mxcsr; __u32 pad2; }; 4.24 KVM_CREATE_IRQCHIP Capability: KVM_CAP_IRQCHIP, KVM_CAP_S390_IRQCHIP (s390) Architectures: x86, ARM, arm64, s390 Type: vm ioctl Parameters: none Returns: 0 on success, -1 on error Creates an interrupt controller model in the kernel. On x86, creates a virtual ioapic, a virtual PIC (two PICs, nested), and sets up future vcpus to have a local APIC. IRQ routing for GSIs 0-15 is set to both PIC and IOAPIC; GSI 16-23 only go to the IOAPIC. On ARM/arm64, a GICv2 is created. Any other GIC versions require the usage of KVM_CREATE_DEVICE, which also supports creating a GICv2. Using KVM_CREATE_DEVICE is preferred over KVM_CREATE_IRQCHIP for GICv2. On s390, a dummy irq routing table is created. Note that on s390 the KVM_CAP_S390_IRQCHIP vm capability needs to be enabled before KVM_CREATE_IRQCHIP can be used. 4.25 KVM_IRQ_LINE Capability: KVM_CAP_IRQCHIP Architectures: x86, arm, arm64 Type: vm ioctl Parameters: struct kvm_irq_level Returns: 0 on success, -1 on error Sets the level of a GSI input to the interrupt controller model in the kernel. On some architectures it is required that an interrupt controller model has been previously created with KVM_CREATE_IRQCHIP. Note that edge-triggered interrupts require the level to be set to 1 and then back to 0. On real hardware, interrupt pins can be active-low or active-high. This does not matter for the level field of struct kvm_irq_level: 1 always means active (asserted), 0 means inactive (deasserted). x86 allows the operating system to program the interrupt polarity (active-low/active-high) for level-triggered interrupts, and KVM used to consider the polarity. However, due to bitrot in the handling of active-low interrupts, the above convention is now valid on x86 too. This is signaled by KVM_CAP_X86_IOAPIC_POLARITY_IGNORED. Userspace should not present interrupts to the guest as active-low unless this capability is present (or unless it is not using the in-kernel irqchip, of course). ARM/arm64 can signal an interrupt either at the CPU level, or at the in-kernel irqchip (GIC), and for in-kernel irqchip can tell the GIC to use PPIs designated for specific cpus. The irq field is interpreted like this:  bits: | 31 ... 24 | 23 ... 16 | 15 ... 0 | field: | irq_type | vcpu_index | irq_id | The irq_type field has the following values: - irq_type[0]: out-of-kernel GIC: irq_id 0 is IRQ, irq_id 1 is FIQ - irq_type[1]: in-kernel GIC: SPI, irq_id between 32 and 1019 (incl.) (the vcpu_index field is ignored) - irq_type[2]: in-kernel GIC: PPI, irq_id between 16 and 31 (incl.) (The irq_id field thus corresponds nicely to the IRQ ID in the ARM GIC specs) In both cases, level is used to assert/deassert the line. struct kvm_irq_level { union { __u32 irq; /* GSI */ __s32 status; /* not used for KVM_IRQ_LEVEL */ }; __u32 level; /* 0 or 1 */ }; 4.26 KVM_GET_IRQCHIP Capability: KVM_CAP_IRQCHIP Architectures: x86 Type: vm ioctl Parameters: struct kvm_irqchip (in/out) Returns: 0 on success, -1 on error Reads the state of a kernel interrupt controller created with KVM_CREATE_IRQCHIP into a buffer provided by the caller. struct kvm_irqchip { __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */ __u32 pad; union { char dummy[512]; /* reserving space */ struct kvm_pic_state pic; struct kvm_ioapic_state ioapic; } chip; }; 4.27 KVM_SET_IRQCHIP Capability: KVM_CAP_IRQCHIP Architectures: x86 Type: vm ioctl Parameters: struct kvm_irqchip (in) Returns: 0 on success, -1 on error Sets the state of a kernel interrupt controller created with KVM_CREATE_IRQCHIP from a buffer provided by the caller. struct kvm_irqchip { __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */ __u32 pad; union { char dummy[512]; /* reserving space */ struct kvm_pic_state pic; struct kvm_ioapic_state ioapic; } chip; }; 4.28 KVM_XEN_HVM_CONFIG Capability: KVM_CAP_XEN_HVM Architectures: x86 Type: vm ioctl Parameters: struct kvm_xen_hvm_config (in) Returns: 0 on success, -1 on error Sets the MSR that the Xen HVM guest uses to initialize its hypercall page, and provides the starting address and size of the hypercall blobs in userspace. When the guest writes the MSR, kvm copies one page of a blob (32- or 64-bit, depending on the vcpu mode) to guest memory. struct kvm_xen_hvm_config { __u32 flags; __u32 msr; __u64 blob_addr_32; __u64 blob_addr_64; __u8 blob_size_32; __u8 blob_size_64; __u8 pad2[30]; }; 4.29 KVM_GET_CLOCK Capability: KVM_CAP_ADJUST_CLOCK Architectures: x86 Type: vm ioctl Parameters: struct kvm_clock_data (out) Returns: 0 on success, -1 on error Gets the current timestamp of kvmclock as seen by the current guest. In conjunction with KVM_SET_CLOCK, it is used to ensure monotonicity on scenarios such as migration. When KVM_CAP_ADJUST_CLOCK is passed to KVM_CHECK_EXTENSION, it returns the set of bits that KVM can return in struct kvm_clock_data's flag member. The only flag defined now is KVM_CLOCK_TSC_STABLE. If set, the returned value is the exact kvmclock value seen by all VCPUs at the instant when KVM_GET_CLOCK was called. If clear, the returned value is simply CLOCK_MONOTONIC plus a constant offset; the offset can be modified with KVM_SET_CLOCK. KVM will try to make all VCPUs follow this clock, but the exact value read by each VCPU could differ, because the host TSC is not stable. struct kvm_clock_data { __u64 clock; /* kvmclock current value */ __u32 flags; __u32 pad[9]; }; 4.30 KVM_SET_CLOCK Capability: KVM_CAP_ADJUST_CLOCK Architectures: x86 Type: vm ioctl Parameters: struct kvm_clock_data (in) Returns: 0 on success, -1 on error Sets the current timestamp of kvmclock to the value specified in its parameter. In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios such as migration. struct kvm_clock_data { __u64 clock; /* kvmclock current value */ __u32 flags; __u32 pad[9]; }; 4.31 KVM_GET_VCPU_EVENTS Capability: KVM_CAP_VCPU_EVENTS Extended by: KVM_CAP_INTR_SHADOW Architectures: x86 Type: vm ioctl Parameters: struct kvm_vcpu_event (out) Returns: 0 on success, -1 on error Gets currently pending exceptions, interrupts, and NMIs as well as related states of the vcpu. struct kvm_vcpu_events { struct { __u8 injected; __u8 nr; __u8 has_error_code; __u8 pad; __u32 error_code; } exception; struct { __u8 injected; __u8 nr; __u8 soft; __u8 shadow; } interrupt; struct { __u8 injected; __u8 pending; __u8 masked; __u8 pad; } nmi; __u32 sipi_vector; __u32 flags; struct { __u8 smm; __u8 pending; __u8 smm_inside_nmi; __u8 latched_init; } smi; }; Only two fields are defined in the flags field: - KVM_VCPUEVENT_VALID_SHADOW may be set in the flags field to signal that interrupt.shadow contains a valid state. - KVM_VCPUEVENT_VALID_SMM may be set in the flags field to signal that smi contains a valid state. 4.32 KVM_SET_VCPU_EVENTS Capability: KVM_CAP_VCPU_EVENTS Extended by: KVM_CAP_INTR_SHADOW Architectures: x86 Type: vm ioctl Parameters: struct kvm_vcpu_event (in) Returns: 0 on success, -1 on error Set pending exceptions, interrupts, and NMIs as well as related states of the vcpu. See KVM_GET_VCPU_EVENTS for the data structure. Fields that may be modified asynchronously by running VCPUs can be excluded from the update. These fields are nmi.pending, sipi_vector, smi.smm, smi.pending. Keep the corresponding bits in the flags field cleared to suppress overwriting the current in-kernel state. The bits are: KVM_VCPUEVENT_VALID_NMI_PENDING - transfer nmi.pending to the kernel KVM_VCPUEVENT_VALID_SIPI_VECTOR - transfer sipi_vector KVM_VCPUEVENT_VALID_SMM - transfer the smi sub-struct. If KVM_CAP_INTR_SHADOW is available, KVM_VCPUEVENT_VALID_SHADOW can be set in the flags field to signal that interrupt.shadow contains a valid state and shall be written into the VCPU. KVM_VCPUEVENT_VALID_SMM can only be set if KVM_CAP_X86_SMM is available. 4.33 KVM_GET_DEBUGREGS Capability: KVM_CAP_DEBUGREGS Architectures: x86 Type: vm ioctl Parameters: struct kvm_debugregs (out) Returns: 0 on success, -1 on error Reads debug registers from the vcpu. struct kvm_debugregs { __u64 db[4]; __u64 dr6; __u64 dr7; __u64 flags; __u64 reserved[9]; }; 4.34 KVM_SET_DEBUGREGS Capability: KVM_CAP_DEBUGREGS Architectures: x86 Type: vm ioctl Parameters: struct kvm_debugregs (in) Returns: 0 on success, -1 on error Writes debug registers into the vcpu. See KVM_GET_DEBUGREGS for the data structure. The flags field is unused yet and must be cleared on entry. 4.35 KVM_SET_USER_MEMORY_REGION Capability: KVM_CAP_USER_MEM Architectures: all Type: vm ioctl Parameters: struct kvm_userspace_memory_region (in) Returns: 0 on success, -1 on error struct kvm_userspace_memory_region { __u32 slot; __u32 flags; __u64 guest_phys_addr; __u64 memory_size; /* bytes */ __u64 userspace_addr; /* start of the userspace allocated memory */ }; /* for kvm_memory_region::flags */ #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0) #define KVM_MEM_READONLY (1UL << 1) This ioctl allows the user to create or modify a guest physical memory slot. When changing an existing slot, it may be moved in the guest physical memory space, or its flags may be modified. It may not be resized. Slots may not overlap in guest physical address space. Bits 0-15 of "slot" specifies the slot id and this value should be less than the maximum number of user memory slots supported per VM. The maximum allowed slots can be queried using KVM_CAP_NR_MEMSLOTS, if this capability is supported by the architecture. If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 of "slot" specifies the address space which is being modified. They must be less than the value that KVM_CHECK_EXTENSION returns for the KVM_CAP_MULTI_ADDRESS_SPACE capability. Slots in separate address spaces are unrelated; the restriction on overlapping slots only applies within each address space. Memory for the region is taken starting at the address denoted by the field userspace_addr, which must point at user addressable memory for the entire memory slot size. Any object may back this memory, including anonymous memory, ordinary files, and hugetlbfs. It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr be identical. This allows large pages in the guest to be backed by large pages in the host. The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it, to make a new slot read-only. In this case, writes to this memory will be posted to userspace as KVM_EXIT_MMIO exits. When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of the memory region are automatically reflected into the guest. For example, an mmap() that affects the region will be made visible immediately. Another example is madvise(MADV_DROP). It is recommended to use this API instead of the KVM_SET_MEMORY_REGION ioctl. The KVM_SET_MEMORY_REGION does not allow fine grained control over memory allocation and is deprecated. 4.36 KVM_SET_TSS_ADDR Capability: KVM_CAP_SET_TSS_ADDR Architectures: x86 Type: vm ioctl Parameters: unsigned long tss_address (in) Returns: 0 on success, -1 on error This ioctl defines the physical address of a three-page region in the guest physical address space. The region must be within the first 4GB of the guest physical address space and must not conflict with any memory slot or any mmio address. The guest may malfunction if it accesses this memory region. This ioctl is required on Intel-based hosts. This is needed on Intel hardware because of a quirk in the virtualization implementation (see the internals documentation when it pops into existence). 4.37 KVM_ENABLE_CAP Capability: KVM_CAP_ENABLE_CAP, KVM_CAP_ENABLE_CAP_VM Architectures: x86 (only KVM_CAP_ENABLE_CAP_VM), mips (only KVM_CAP_ENABLE_CAP), ppc, s390 Type: vcpu ioctl, vm ioctl (with KVM_CAP_ENABLE_CAP_VM) Parameters: struct kvm_enable_cap (in) Returns: 0 on success; -1 on error +Not all extensions are enabled by default. Using this ioctl the application can enable an extension, making it available to the guest. On systems that do not support this ioctl, it always fails. On systems that do support it, it only works for extensions that are supported for enablement. To check if a capability can be enabled, the KVM_CHECK_EXTENSION ioctl should be used. struct kvm_enable_cap { /* in */ __u32 cap; The capability that is supposed to get enabled. __u32 flags; A bitfield indicating future enhancements. Has to be 0 for now. __u64 args[4]; Arguments for enabling a feature. If a feature needs initial values to function properly, this is the place to put them. __u8 pad[64]; }; The vcpu ioctl should be used for vcpu-specific capabilities, the vm ioctl for vm-wide capabilities. 4.38 KVM_GET_MP_STATE Capability: KVM_CAP_MP_STATE Architectures: x86, s390, arm, arm64 Type: vcpu ioctl Parameters: struct kvm_mp_state (out) Returns: 0 on success; -1 on error struct kvm_mp_state { __u32 mp_state; }; Returns the vcpu's current "multiprocessing state" (though also valid on uniprocessor guests). Possible values are: - KVM_MP_STATE_RUNNABLE: the vcpu is currently running [x86,arm/arm64] - KVM_MP_STATE_UNINITIALIZED: the vcpu is an application processor (AP) which has not yet received an INIT signal [x86] - KVM_MP_STATE_INIT_RECEIVED: the vcpu has received an INIT signal, and is now ready for a SIPI [x86] - KVM_MP_STATE_HALTED: the vcpu has executed a HLT instruction and is waiting for an interrupt [x86] - KVM_MP_STATE_SIPI_RECEIVED: the vcpu has just received a SIPI (vector accessible via KVM_GET_VCPU_EVENTS) [x86] - KVM_MP_STATE_STOPPED: the vcpu is stopped [s390,arm/arm64] - KVM_MP_STATE_CHECK_STOP: the vcpu is in a special error state [s390] - KVM_MP_STATE_OPERATING: the vcpu is operating (running or halted) [s390] - KVM_MP_STATE_LOAD: the vcpu is in a special load/startup state [s390] On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an in-kernel irqchip, the multiprocessing state must be maintained by userspace on these architectures. For arm/arm64: The only states that are valid are KVM_MP_STATE_STOPPED and KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not. 4.39 KVM_SET_MP_STATE Capability: KVM_CAP_MP_STATE Architectures: x86, s390, arm, arm64 Type: vcpu ioctl Parameters: struct kvm_mp_state (in) Returns: 0 on success; -1 on error Sets the vcpu's current "multiprocessing state"; see KVM_GET_MP_STATE for arguments. On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an in-kernel irqchip, the multiprocessing state must be maintained by userspace on these architectures. For arm/arm64: The only states that are valid are KVM_MP_STATE_STOPPED and KVM_MP_STATE_RUNNABLE which reflect if the vcpu should be paused or not. 4.40 KVM_SET_IDENTITY_MAP_ADDR Capability: KVM_CAP_SET_IDENTITY_MAP_ADDR Architectures: x86 Type: vm ioctl Parameters: unsigned long identity (in) Returns: 0 on success, -1 on error This ioctl defines the physical address of a one-page region in the guest physical address space. The region must be within the first 4GB of the guest physical address space and must not conflict with any memory slot or any mmio address. The guest may malfunction if it accesses this memory region. Setting the address to 0 will result in resetting the address to its default (0xfffbc000). This ioctl is required on Intel-based hosts. This is needed on Intel hardware because of a quirk in the virtualization implementation (see the internals documentation when it pops into existence). Fails if any VCPU has already been created. 4.41 KVM_SET_BOOT_CPU_ID Capability: KVM_CAP_SET_BOOT_CPU_ID Architectures: x86 Type: vm ioctl Parameters: unsigned long vcpu_id Returns: 0 on success, -1 on error Define which vcpu is the Bootstrap Processor (BSP). Values are the same as the vcpu id in KVM_CREATE_VCPU. If this ioctl is not called, the default is vcpu 0. 4.42 KVM_GET_XSAVE Capability: KVM_CAP_XSAVE Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_xsave (out) Returns: 0 on success, -1 on error struct kvm_xsave { __u32 region[1024]; }; This ioctl would copy current vcpu's xsave struct to the userspace. 4.43 KVM_SET_XSAVE Capability: KVM_CAP_XSAVE Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_xsave (in) Returns: 0 on success, -1 on error struct kvm_xsave { __u32 region[1024]; }; This ioctl would copy userspace's xsave struct to the kernel. 4.44 KVM_GET_XCRS Capability: KVM_CAP_XCRS Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_xcrs (out) Returns: 0 on success, -1 on error struct kvm_xcr { __u32 xcr; __u32 reserved; __u64 value; }; struct kvm_xcrs { __u32 nr_xcrs; __u32 flags; struct kvm_xcr xcrs[KVM_MAX_XCRS]; __u64 padding[16]; }; This ioctl would copy current vcpu's xcrs to the userspace. 4.45 KVM_SET_XCRS Capability: KVM_CAP_XCRS Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_xcrs (in) Returns: 0 on success, -1 on error struct kvm_xcr { __u32 xcr; __u32 reserved; __u64 value; }; struct kvm_xcrs { __u32 nr_xcrs; __u32 flags; struct kvm_xcr xcrs[KVM_MAX_XCRS]; __u64 padding[16]; }; This ioctl would set vcpu's xcr to the value userspace specified. 4.46 KVM_GET_SUPPORTED_CPUID Capability: KVM_CAP_EXT_CPUID Architectures: x86 Type: system ioctl Parameters: struct kvm_cpuid2 (in/out) Returns: 0 on success, -1 on error struct kvm_cpuid2 { __u32 nent; __u32 padding; struct kvm_cpuid_entry2 entries[0]; }; #define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0) #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1) #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2) struct kvm_cpuid_entry2 { __u32 function; __u32 index; __u32 flags; __u32 eax; __u32 ebx; __u32 ecx; __u32 edx; __u32 padding[3]; }; This ioctl returns x86 cpuid features which are supported by both the hardware and kvm. Userspace can use the information returned by this ioctl to construct cpuid information (for KVM_SET_CPUID2) that is consistent with hardware, kernel, and userspace capabilities, and with user requirements (for example, the user may wish to constrain cpuid to emulate older hardware, or for feature consistency across a cluster). Userspace invokes KVM_GET_SUPPORTED_CPUID by passing a kvm_cpuid2 structure with the 'nent' field indicating the number of entries in the variable-size array 'entries'. If the number of entries is too low to describe the cpu capabilities, an error (E2BIG) is returned. If the number is too high, the 'nent' field is adjusted and an error (ENOMEM) is returned. If the number is just right, the 'nent' field is adjusted to the number of valid entries in the 'entries' array, which is then filled. The entries returned are the host cpuid as returned by the cpuid instruction, with unknown or unsupported features masked out. Some features (for example, x2apic), may not be present in the host cpu, but are exposed by kvm if it can emulate them efficiently. The fields in each entry are defined as follows: function: the eax value used to obtain the entry index: the ecx value used to obtain the entry (for entries that are affected by ecx) flags: an OR of zero or more of the following: KVM_CPUID_FLAG_SIGNIFCANT_INDEX: if the index field is valid KVM_CPUID_FLAG_STATEFUL_FUNC: if cpuid for this function returns different values for successive invocations; there will be several entries with the same function, all with this flag set KVM_CPUID_FLAG_STATE_READ_NEXT: for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is the first entry to be read by a cpu eax, ebx, ecx, edx: the values returned by the cpuid instruction for this function/index combination The TSC deadline timer feature (CPUID leaf 1, ecx[24]) is always returned as false, since the feature depends on KVM_CREATE_IRQCHIP for local APIC support. Instead it is reported via ioctl(KVM_CHECK_EXTENSION, KVM_CAP_TSC_DEADLINE_TIMER) if that returns true and you use KVM_CREATE_IRQCHIP, or if you emulate the feature in userspace, then you can enable the feature for KVM_SET_CPUID2. 4.47 KVM_PPC_GET_PVINFO Capability: KVM_CAP_PPC_GET_PVINFO Architectures: ppc Type: vm ioctl Parameters: struct kvm_ppc_pvinfo (out) Returns: 0 on success, !0 on error struct kvm_ppc_pvinfo { __u32 flags; __u32 hcall[4]; __u8 pad[108]; }; This ioctl fetches PV specific information that need to be passed to the guest using the device tree or other means from vm context. The hcall array defines 4 instructions that make up a hypercall. If any additional field gets added to this structure later on, a bit for that additional piece of information will be set in the flags bitmap. The flags bitmap is defined as: /* the host supports the ePAPR idle hcall #define KVM_PPC_PVINFO_FLAGS_EV_IDLE (1<<0) 4.52 KVM_SET_GSI_ROUTING Capability: KVM_CAP_IRQ_ROUTING Architectures: x86 s390 arm arm64 Type: vm ioctl Parameters: struct kvm_irq_routing (in) Returns: 0 on success, -1 on error Sets the GSI routing table entries, overwriting any previously set entries. On arm/arm64, GSI routing has the following limitation: - GSI routing does not apply to KVM_IRQ_LINE but only to KVM_IRQFD. struct kvm_irq_routing { __u32 nr; __u32 flags; struct kvm_irq_routing_entry entries[0]; }; No flags are specified so far, the corresponding field must be set to zero. struct kvm_irq_routing_entry { __u32 gsi; __u32 type; __u32 flags; __u32 pad; union { struct kvm_irq_routing_irqchip irqchip; struct kvm_irq_routing_msi msi; struct kvm_irq_routing_s390_adapter adapter; struct kvm_irq_routing_hv_sint hv_sint; __u32 pad[8]; } u; }; /* gsi routing entry types */ #define KVM_IRQ_ROUTING_IRQCHIP 1 #define KVM_IRQ_ROUTING_MSI 2 #define KVM_IRQ_ROUTING_S390_ADAPTER 3 #define KVM_IRQ_ROUTING_HV_SINT 4 flags: - KVM_MSI_VALID_DEVID: used along with KVM_IRQ_ROUTING_MSI routing entry type, specifies that the devid field contains a valid value. The per-VM KVM_CAP_MSI_DEVID capability advertises the requirement to provide the device ID. If this capability is not available, userspace should never set the KVM_MSI_VALID_DEVID flag as the ioctl might fail. - zero otherwise struct kvm_irq_routing_irqchip { __u32 irqchip; __u32 pin; }; struct kvm_irq_routing_msi { __u32 address_lo; __u32 address_hi; __u32 data; union { __u32 pad; __u32 devid; }; }; If KVM_MSI_VALID_DEVID is set, devid contains a unique device identifier for the device that wrote the MSI message. For PCI, this is usually a BFD identifier in the lower 16 bits. On x86, address_hi is ignored unless the KVM_X2APIC_API_USE_32BIT_IDS feature of KVM_CAP_X2APIC_API capability is enabled. If it is enabled, address_hi bits 31-8 provide bits 31-8 of the destination id. Bits 7-0 of address_hi must be zero. struct kvm_irq_routing_s390_adapter { __u64 ind_addr; __u64 summary_addr; __u64 ind_offset; __u32 summary_offset; __u32 adapter_id; }; struct kvm_irq_routing_hv_sint { __u32 vcpu; __u32 sint; }; 4.55 KVM_SET_TSC_KHZ Capability: KVM_CAP_TSC_CONTROL Architectures: x86 Type: vcpu ioctl Parameters: virtual tsc_khz Returns: 0 on success, -1 on error Specifies the tsc frequency for the virtual machine. The unit of the frequency is KHz. 4.56 KVM_GET_TSC_KHZ Capability: KVM_CAP_GET_TSC_KHZ Architectures: x86 Type: vcpu ioctl Parameters: none Returns: virtual tsc-khz on success, negative value on error Returns the tsc frequency of the guest. The unit of the return value is KHz. If the host has unstable tsc this ioctl returns -EIO instead as an error. 4.57 KVM_GET_LAPIC Capability: KVM_CAP_IRQCHIP Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_lapic_state (out) Returns: 0 on success, -1 on error #define KVM_APIC_REG_SIZE 0x400 struct kvm_lapic_state { char regs[KVM_APIC_REG_SIZE]; }; Reads the Local APIC registers and copies them into the input argument. The data format and layout are the same as documented in the architecture manual. If KVM_X2APIC_API_USE_32BIT_IDS feature of KVM_CAP_X2APIC_API is enabled, then the format of APIC_ID register depends on the APIC mode (reported by MSR_IA32_APICBASE) of its VCPU. x2APIC stores APIC ID in the APIC_ID register (bytes 32-35). xAPIC only allows an 8-bit APIC ID which is stored in bits 31-24 of the APIC register, or equivalently in byte 35 of struct kvm_lapic_state's regs field. KVM_GET_LAPIC must then be called after MSR_IA32_APICBASE has been set with KVM_SET_MSR. If KVM_X2APIC_API_USE_32BIT_IDS feature is disabled, struct kvm_lapic_state always uses xAPIC format. 4.58 KVM_SET_LAPIC Capability: KVM_CAP_IRQCHIP Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_lapic_state (in) Returns: 0 on success, -1 on error #define KVM_APIC_REG_SIZE 0x400 struct kvm_lapic_state { char regs[KVM_APIC_REG_SIZE]; }; Copies the input argument into the Local APIC registers. The data format and layout are the same as documented in the architecture manual. The format of the APIC ID register (bytes 32-35 of struct kvm_lapic_state's regs field) depends on the state of the KVM_CAP_X2APIC_API capability. See the note in KVM_GET_LAPIC. 4.59 KVM_IOEVENTFD Capability: KVM_CAP_IOEVENTFD Architectures: all Type: vm ioctl Parameters: struct kvm_ioeventfd (in) Returns: 0 on success, !0 on error This ioctl attaches or detaches an ioeventfd to a legal pio/mmio address within the guest. A guest write in the registered address will signal the provided event instead of triggering an exit. struct kvm_ioeventfd { __u64 datamatch; __u64 addr; /* legal pio/mmio address */ __u32 len; /* 0, 1, 2, 4, or 8 bytes */ __s32 fd; __u32 flags; __u8 pad[36]; }; For the special case of virtio-ccw devices on s390, the ioevent is matched to a subchannel/virtqueue tuple instead. The following flags are defined: #define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch) #define KVM_IOEVENTFD_FLAG_PIO (1 << kvm_ioeventfd_flag_nr_pio) #define KVM_IOEVENTFD_FLAG_DEASSIGN (1 << kvm_ioeventfd_flag_nr_deassign) #define KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY \ (1 << kvm_ioeventfd_flag_nr_virtio_ccw_notify) If datamatch flag is set, the event will be signaled only if the written value to the registered address is equal to datamatch in struct kvm_ioeventfd. For virtio-ccw devices, addr contains the subchannel id and datamatch the virtqueue index. With KVM_CAP_IOEVENTFD_ANY_LENGTH, a zero length ioeventfd is allowed, and the kernel will ignore the length of guest write and may get a faster vmexit. The speedup may only apply to specific architectures, but the ioeventfd will work anyway. 4.60 KVM_DIRTY_TLB Capability: KVM_CAP_SW_TLB Architectures: ppc Type: vcpu ioctl Parameters: struct kvm_dirty_tlb (in) Returns: 0 on success, -1 on error struct kvm_dirty_tlb { __u64 bitmap; __u32 num_dirty; }; This must be called whenever userspace has changed an entry in the shared TLB, prior to calling KVM_RUN on the associated vcpu. The "bitmap" field is the userspace address of an array. This array consists of a number of bits, equal to the total number of TLB entries as determined by the last successful call to KVM_CONFIG_TLB, rounded up to the nearest multiple of 64. Each bit corresponds to one TLB entry, ordered the same as in the shared TLB array. The array is little-endian: the bit 0 is the least significant bit of the first byte, bit 8 is the least significant bit of the second byte, etc. This avoids any complications with differing word sizes. The "num_dirty" field is a performance hint for KVM to determine whether it should skip processing the bitmap and just invalidate everything. It must be set to the number of set bits in the bitmap. 4.62 KVM_CREATE_SPAPR_TCE Capability: KVM_CAP_SPAPR_TCE Architectures: powerpc Type: vm ioctl Parameters: struct kvm_create_spapr_tce (in) Returns: file descriptor for manipulating the created TCE table This creates a virtual TCE (translation control entry) table, which is an IOMMU for PAPR-style virtual I/O. It is used to translate logical addresses used in virtual I/O into guest physical addresses, and provides a scatter/gather capability for PAPR virtual I/O. /* for KVM_CAP_SPAPR_TCE */ struct kvm_create_spapr_tce { __u64 liobn; __u32 window_size; }; The liobn field gives the logical IO bus number for which to create a TCE table. The window_size field specifies the size of the DMA window which this TCE table will translate - the table will contain one 64 bit TCE entry for every 4kiB of the DMA window. When the guest issues an H_PUT_TCE hcall on a liobn for which a TCE table has been created using this ioctl(), the kernel will handle it in real mode, updating the TCE table. H_PUT_TCE calls for other liobns will cause a vm exit and must be handled by userspace. The return value is a file descriptor which can be passed to mmap(2) to map the created TCE table into userspace. This lets userspace read the entries written by kernel-handled H_PUT_TCE calls, and also lets userspace update the TCE table directly which is useful in some circumstances. 4.63 KVM_ALLOCATE_RMA Capability: KVM_CAP_PPC_RMA Architectures: powerpc Type: vm ioctl Parameters: struct kvm_allocate_rma (out) Returns: file descriptor for mapping the allocated RMA This allocates a Real Mode Area (RMA) from the pool allocated at boot time by the kernel. An RMA is a physically-contiguous, aligned region of memory used on older POWER processors to provide the memory which will be accessed by real-mode (MMU off) accesses in a KVM guest. POWER processors support a set of sizes for the RMA that usually includes 64MB, 128MB, 256MB and some larger powers of two. /* for KVM_ALLOCATE_RMA */ struct kvm_allocate_rma { __u64 rma_size; }; The return value is a file descriptor which can be passed to mmap(2) to map the allocated RMA into userspace. The mapped area can then be passed to the KVM_SET_USER_MEMORY_REGION ioctl to establish it as the RMA for a virtual machine. The size of the RMA in bytes (which is fixed at host kernel boot time) is returned in the rma_size field of the argument structure. The KVM_CAP_PPC_RMA capability is 1 or 2 if the KVM_ALLOCATE_RMA ioctl is supported; 2 if the processor requires all virtual machines to have an RMA, or 1 if the processor can use an RMA but doesn't require it, because it supports the Virtual RMA (VRMA) facility. 4.64 KVM_NMI Capability: KVM_CAP_USER_NMI Architectures: x86 Type: vcpu ioctl Parameters: none Returns: 0 on success, -1 on error Queues an NMI on the thread's vcpu. Note this is well defined only when KVM_CREATE_IRQCHIP has not been called, since this is an interface between the virtual cpu core and virtual local APIC. After KVM_CREATE_IRQCHIP has been called, this interface is completely emulated within the kernel. To use this to emulate the LINT1 input with KVM_CREATE_IRQCHIP, use the following algorithm: - pause the vcpu - read the local APIC's state (KVM_GET_LAPIC) - check whether changing LINT1 will queue an NMI (see the LVT entry for LINT1) - if so, issue KVM_NMI - resume the vcpu Some guests configure the LINT1 NMI input to cause a panic, aiding in debugging. 4.65 KVM_S390_UCAS_MAP Capability: KVM_CAP_S390_UCONTROL Architectures: s390 Type: vcpu ioctl Parameters: struct kvm_s390_ucas_mapping (in) Returns: 0 in case of success The parameter is defined like this: struct kvm_s390_ucas_mapping { __u64 user_addr; __u64 vcpu_addr; __u64 length; }; This ioctl maps the memory at "user_addr" with the length "length" to the vcpu's address space starting at "vcpu_addr". All parameters need to be aligned by 1 megabyte. 4.66 KVM_S390_UCAS_UNMAP Capability: KVM_CAP_S390_UCONTROL Architectures: s390 Type: vcpu ioctl Parameters: struct kvm_s390_ucas_mapping (in) Returns: 0 in case of success The parameter is defined like this: struct kvm_s390_ucas_mapping { __u64 user_addr; __u64 vcpu_addr; __u64 length; }; This ioctl unmaps the memory in the vcpu's address space starting at "vcpu_addr" with the length "length". The field "user_addr" is ignored. All parameters need to be aligned by 1 megabyte. 4.67 KVM_S390_VCPU_FAULT Capability: KVM_CAP_S390_UCONTROL Architectures: s390 Type: vcpu ioctl Parameters: vcpu absolute address (in) Returns: 0 in case of success This call creates a page table entry on the virtual cpu's address space (for user controlled virtual machines) or the virtual machine's address space (for regular virtual machines). This only works for minor faults, thus it's recommended to access subject memory page via the user page table upfront. This is useful to handle validity intercepts for user controlled virtual machines to fault in the virtual cpu's lowcore pages prior to calling the KVM_RUN ioctl. 4.68 KVM_SET_ONE_REG Capability: KVM_CAP_ONE_REG Architectures: all Type: vcpu ioctl Parameters: struct kvm_one_reg (in) Returns: 0 on success, negative value on failure struct kvm_one_reg { __u64 id; __u64 addr; }; Using this ioctl, a single vcpu register can be set to a specific value defined by user space with the passed in struct kvm_one_reg, where id refers to the register identifier as described below and addr is a pointer to a variable with the respective size. There can be architecture agnostic and architecture specific registers. Each have their own range of operation and their own constants and width. To keep track of the implemented registers, find a list below: Arch | Register | Width (bits) | | PPC | KVM_REG_PPC_HIOR | 64 PPC | KVM_REG_PPC_IAC1 | 64 PPC | KVM_REG_PPC_IAC2 | 64 PPC | KVM_REG_PPC_IAC3 | 64 PPC | KVM_REG_PPC_IAC4 | 64 PPC | KVM_REG_PPC_DAC1 | 64 PPC | KVM_REG_PPC_DAC2 | 64 PPC | KVM_REG_PPC_DABR | 64 PPC | KVM_REG_PPC_DSCR | 64 PPC | KVM_REG_PPC_PURR | 64 PPC | KVM_REG_PPC_SPURR | 64 PPC | KVM_REG_PPC_DAR | 64 PPC | KVM_REG_PPC_DSISR | 32 PPC | KVM_REG_PPC_AMR | 64 PPC | KVM_REG_PPC_UAMOR | 64 PPC | KVM_REG_PPC_MMCR0 | 64 PPC | KVM_REG_PPC_MMCR1 | 64 PPC | KVM_REG_PPC_MMCRA | 64 PPC | KVM_REG_PPC_MMCR2 | 64 PPC | KVM_REG_PPC_MMCRS | 64 PPC | KVM_REG_PPC_SIAR | 64 PPC | KVM_REG_PPC_SDAR | 64 PPC | KVM_REG_PPC_SIER | 64 PPC | KVM_REG_PPC_PMC1 | 32 PPC | KVM_REG_PPC_PMC2 | 32 PPC | KVM_REG_PPC_PMC3 | 32 PPC | KVM_REG_PPC_PMC4 | 32 PPC | KVM_REG_PPC_PMC5 | 32 PPC | KVM_REG_PPC_PMC6 | 32 PPC | KVM_REG_PPC_PMC7 | 32 PPC | KVM_REG_PPC_PMC8 | 32 PPC | KVM_REG_PPC_FPR0 | 64 ... PPC | KVM_REG_PPC_FPR31 | 64 PPC | KVM_REG_PPC_VR0 | 128 ... PPC | KVM_REG_PPC_VR31 | 128 PPC | KVM_REG_PPC_VSR0 | 128 ... PPC | KVM_REG_PPC_VSR31 | 128 PPC | KVM_REG_PPC_FPSCR | 64 PPC | KVM_REG_PPC_VSCR | 32 PPC | KVM_REG_PPC_VPA_ADDR | 64 PPC | KVM_REG_PPC_VPA_SLB | 128 PPC | KVM_REG_PPC_VPA_DTL | 128 PPC | KVM_REG_PPC_EPCR | 32 PPC | KVM_REG_PPC_EPR | 32 PPC | KVM_REG_PPC_TCR | 32 PPC | KVM_REG_PPC_TSR | 32 PPC | KVM_REG_PPC_OR_TSR | 32 PPC | KVM_REG_PPC_CLEAR_TSR | 32 PPC | KVM_REG_PPC_MAS0 | 32 PPC | KVM_REG_PPC_MAS1 | 32 PPC | KVM_REG_PPC_MAS2 | 64 PPC | KVM_REG_PPC_MAS7_3 | 64 PPC | KVM_REG_PPC_MAS4 | 32 PPC | KVM_REG_PPC_MAS6 | 32 PPC | KVM_REG_PPC_MMUCFG | 32 PPC | KVM_REG_PPC_TLB0CFG | 32 PPC | KVM_REG_PPC_TLB1CFG | 32 PPC | KVM_REG_PPC_TLB2CFG | 32 PPC | KVM_REG_PPC_TLB3CFG | 32 PPC | KVM_REG_PPC_TLB0PS | 32 PPC | KVM_REG_PPC_TLB1PS | 32 PPC | KVM_REG_PPC_TLB2PS | 32 PPC | KVM_REG_PPC_TLB3PS | 32 PPC | KVM_REG_PPC_EPTCFG | 32 PPC | KVM_REG_PPC_ICP_STATE | 64 PPC | KVM_REG_PPC_TB_OFFSET | 64 PPC | KVM_REG_PPC_SPMC1 | 32 PPC | KVM_REG_PPC_SPMC2 | 32 PPC | KVM_REG_PPC_IAMR | 64 PPC | KVM_REG_PPC_TFHAR | 64 PPC | KVM_REG_PPC_TFIAR | 64 PPC | KVM_REG_PPC_TEXASR | 64 PPC | KVM_REG_PPC_FSCR | 64 PPC | KVM_REG_PPC_PSPB | 32 PPC | KVM_REG_PPC_EBBHR | 64 PPC | KVM_REG_PPC_EBBRR | 64 PPC | KVM_REG_PPC_BESCR | 64 PPC | KVM_REG_PPC_TAR | 64 PPC | KVM_REG_PPC_DPDES | 64 PPC | KVM_REG_PPC_DAWR | 64 PPC | KVM_REG_PPC_DAWRX | 64 PPC | KVM_REG_PPC_CIABR | 64 PPC | KVM_REG_PPC_IC | 64 PPC | KVM_REG_PPC_VTB | 64 PPC | KVM_REG_PPC_CSIGR | 64 PPC | KVM_REG_PPC_TACR | 64 PPC | KVM_REG_PPC_TCSCR | 64 PPC | KVM_REG_PPC_PID | 64 PPC | KVM_REG_PPC_ACOP | 64 PPC | KVM_REG_PPC_VRSAVE | 32 PPC | KVM_REG_PPC_LPCR | 32 PPC | KVM_REG_PPC_LPCR_64 | 64 PPC | KVM_REG_PPC_PPR | 64 PPC | KVM_REG_PPC_ARCH_COMPAT | 32 PPC | KVM_REG_PPC_DABRX | 32 PPC | KVM_REG_PPC_WORT | 64 PPC | KVM_REG_PPC_SPRG9 | 64 PPC | KVM_REG_PPC_DBSR | 32 PPC | KVM_REG_PPC_TIDR | 64 PPC | KVM_REG_PPC_PSSCR | 64 PPC | KVM_REG_PPC_DEC_EXPIRY | 64 PPC | KVM_REG_PPC_TM_GPR0 | 64 ... PPC | KVM_REG_PPC_TM_GPR31 | 64 PPC | KVM_REG_PPC_TM_VSR0 | 128 ... PPC | KVM_REG_PPC_TM_VSR63 | 128 PPC | KVM_REG_PPC_TM_CR | 64 PPC | KVM_REG_PPC_TM_LR | 64 PPC | KVM_REG_PPC_TM_CTR | 64 PPC | KVM_REG_PPC_TM_FPSCR | 64 PPC | KVM_REG_PPC_TM_AMR | 64 PPC | KVM_REG_PPC_TM_PPR | 64 PPC | KVM_REG_PPC_TM_VRSAVE | 64 PPC | KVM_REG_PPC_TM_VSCR | 32 PPC | KVM_REG_PPC_TM_DSCR | 64 PPC | KVM_REG_PPC_TM_TAR | 64 PPC | KVM_REG_PPC_TM_XER | 64 | | MIPS | KVM_REG_MIPS_R0 | 64 ... MIPS | KVM_REG_MIPS_R31 | 64 MIPS | KVM_REG_MIPS_HI | 64 MIPS | KVM_REG_MIPS_LO | 64 MIPS | KVM_REG_MIPS_PC | 64 MIPS | KVM_REG_MIPS_CP0_INDEX | 32 MIPS | KVM_REG_MIPS_CP0_ENTRYLO0 | 64 MIPS | KVM_REG_MIPS_CP0_ENTRYLO1 | 64 MIPS | KVM_REG_MIPS_CP0_CONTEXT | 64 MIPS | KVM_REG_MIPS_CP0_CONTEXTCONFIG| 32 MIPS | KVM_REG_MIPS_CP0_USERLOCAL | 64 MIPS | KVM_REG_MIPS_CP0_XCONTEXTCONFIG| 64 MIPS | KVM_REG_MIPS_CP0_PAGEMASK | 32 MIPS | KVM_REG_MIPS_CP0_PAGEGRAIN | 32 MIPS | KVM_REG_MIPS_CP0_SEGCTL0 | 64 MIPS | KVM_REG_MIPS_CP0_SEGCTL1 | 64 MIPS | KVM_REG_MIPS_CP0_SEGCTL2 | 64 MIPS | KVM_REG_MIPS_CP0_PWBASE | 64 MIPS | KVM_REG_MIPS_CP0_PWFIELD | 64 MIPS | KVM_REG_MIPS_CP0_PWSIZE | 64 MIPS | KVM_REG_MIPS_CP0_WIRED | 32 MIPS | KVM_REG_MIPS_CP0_PWCTL | 32 MIPS | KVM_REG_MIPS_CP0_HWRENA | 32 MIPS | KVM_REG_MIPS_CP0_BADVADDR | 64 MIPS | KVM_REG_MIPS_CP0_BADINSTR | 32 MIPS | KVM_REG_MIPS_CP0_BADINSTRP | 32 MIPS | KVM_REG_MIPS_CP0_COUNT | 32 MIPS | KVM_REG_MIPS_CP0_ENTRYHI | 64 MIPS | KVM_REG_MIPS_CP0_COMPARE | 32 MIPS | KVM_REG_MIPS_CP0_STATUS | 32 MIPS | KVM_REG_MIPS_CP0_INTCTL | 32 MIPS | KVM_REG_MIPS_CP0_CAUSE | 32 MIPS | KVM_REG_MIPS_CP0_EPC | 64 MIPS | KVM_REG_MIPS_CP0_PRID | 32 MIPS | KVM_REG_MIPS_CP0_EBASE | 64 MIPS | KVM_REG_MIPS_CP0_CONFIG | 32 MIPS | KVM_REG_MIPS_CP0_CONFIG1 | 32 MIPS | KVM_REG_MIPS_CP0_CONFIG2 | 32 MIPS | KVM_REG_MIPS_CP0_CONFIG3 | 32 MIPS | KVM_REG_MIPS_CP0_CONFIG4 | 32 MIPS | KVM_REG_MIPS_CP0_CONFIG5 | 32 MIPS | KVM_REG_MIPS_CP0_CONFIG7 | 32 MIPS | KVM_REG_MIPS_CP0_XCONTEXT | 64 MIPS | KVM_REG_MIPS_CP0_ERROREPC | 64 MIPS | KVM_REG_MIPS_CP0_KSCRATCH1 | 64 MIPS | KVM_REG_MIPS_CP0_KSCRATCH2 | 64 MIPS | KVM_REG_MIPS_CP0_KSCRATCH3 | 64 MIPS | KVM_REG_MIPS_CP0_KSCRATCH4 | 64 MIPS | KVM_REG_MIPS_CP0_KSCRATCH5 | 64 MIPS | KVM_REG_MIPS_CP0_KSCRATCH6 | 64 MIPS | KVM_REG_MIPS_CP0_MAAR(0..63) | 64 MIPS | KVM_REG_MIPS_COUNT_CTL | 64 MIPS | KVM_REG_MIPS_COUNT_RESUME | 64 MIPS | KVM_REG_MIPS_COUNT_HZ | 64 MIPS | KVM_REG_MIPS_FPR_32(0..31) | 32 MIPS | KVM_REG_MIPS_FPR_64(0..31) | 64 MIPS | KVM_REG_MIPS_VEC_128(0..31) | 128 MIPS | KVM_REG_MIPS_FCR_IR | 32 MIPS | KVM_REG_MIPS_FCR_CSR | 32 MIPS | KVM_REG_MIPS_MSA_IR | 32 MIPS | KVM_REG_MIPS_MSA_CSR | 32 ARM registers are mapped using the lower 32 bits. The upper 16 of that is the register group type, or coprocessor number: ARM core registers have the following id bit patterns: 0x4020 0000 0010 ARM 32-bit CP15 registers have the following id bit patterns: 0x4020 0000 000F ARM 64-bit CP15 registers have the following id bit patterns: 0x4030 0000 000F ARM CCSIDR registers are demultiplexed by CSSELR value: 0x4020 0000 0011 00 ARM 32-bit VFP control registers have the following id bit patterns: 0x4020 0000 0012 1 ARM 64-bit FP registers have the following id bit patterns: 0x4030 0000 0012 0 arm64 registers are mapped using the lower 32 bits. The upper 16 of that is the register group type, or coprocessor number: arm64 core/FP-SIMD registers have the following id bit patterns. Note that the size of the access is variable, as the kvm_regs structure contains elements ranging from 32 to 128 bits. The index is a 32bit value in the kvm_regs structure seen as a 32bit array. 0x60x0 0000 0010 arm64 CCSIDR registers are demultiplexed by CSSELR value: 0x6020 0000 0011 00 arm64 system registers have the following id bit patterns: 0x6030 0000 0013 MIPS registers are mapped using the lower 32 bits. The upper 16 of that is the register group type: MIPS core registers (see above) have the following id bit patterns: 0x7030 0000 0000 MIPS CP0 registers (see KVM_REG_MIPS_CP0_* above) have the following id bit patterns depending on whether they're 32-bit or 64-bit registers: 0x7020 0000 0001 00 (32-bit) 0x7030 0000 0001 00 (64-bit) Note: KVM_REG_MIPS_CP0_ENTRYLO0 and KVM_REG_MIPS_CP0_ENTRYLO1 are the MIPS64 versions of the EntryLo registers regardless of the word size of the host hardware, host kernel, guest, and whether XPA is present in the guest, i.e. with the RI and XI bits (if they exist) in bits 63 and 62 respectively, and the PFNX field starting at bit 30. MIPS MAARs (see KVM_REG_MIPS_CP0_MAAR(*) above) have the following id bit patterns: 0x7030 0000 0001 01 MIPS KVM control registers (see above) have the following id bit patterns: 0x7030 0000 0002 MIPS FPU registers (see KVM_REG_MIPS_FPR_{32,64}() above) have the following id bit patterns depending on the size of the register being accessed. They are always accessed according to the current guest FPU mode (Status.FR and Config5.FRE), i.e. as the guest would see them, and they become unpredictable if the guest FPU mode is changed. MIPS SIMD Architecture (MSA) vector registers (see KVM_REG_MIPS_VEC_128() above) have similar patterns as they overlap the FPU registers: 0x7020 0000 0003 00 <0:3> (32-bit FPU registers) 0x7030 0000 0003 00 <0:3> (64-bit FPU registers) 0x7040 0000 0003 00 <0:3> (128-bit MSA vector registers) MIPS FPU control registers (see KVM_REG_MIPS_FCR_{IR,CSR} above) have the following id bit patterns: 0x7020 0000 0003 01 <0:3> MIPS MSA control registers (see KVM_REG_MIPS_MSA_{IR,CSR} above) have the following id bit patterns: 0x7020 0000 0003 02 <0:3> 4.69 KVM_GET_ONE_REG Capability: KVM_CAP_ONE_REG Architectures: all Type: vcpu ioctl Parameters: struct kvm_one_reg (in and out) Returns: 0 on success, negative value on failure This ioctl allows to receive the value of a single register implemented in a vcpu. The register to read is indicated by the "id" field of the kvm_one_reg struct passed in. On success, the register value can be found at the memory location pointed to by "addr". The list of registers accessible using this interface is identical to the list in 4.68. 4.70 KVM_KVMCLOCK_CTRL Capability: KVM_CAP_KVMCLOCK_CTRL Architectures: Any that implement pvclocks (currently x86 only) Type: vcpu ioctl Parameters: None Returns: 0 on success, -1 on error This signals to the host kernel that the specified guest is being paused by userspace. The host will set a flag in the pvclock structure that is checked from the soft lockup watchdog. The flag is part of the pvclock structure that is shared between guest and host, specifically the second bit of the flags field of the pvclock_vcpu_time_info structure. It will be set exclusively by the host and read/cleared exclusively by the guest. The guest operation of checking and clearing the flag must an atomic operation so load-link/store-conditional, or equivalent must be used. There are two cases where the guest will clear the flag: when the soft lockup watchdog timer resets itself or when a soft lockup is detected. This ioctl can be called any time after pausing the vcpu, but before it is resumed. 4.71 KVM_SIGNAL_MSI Capability: KVM_CAP_SIGNAL_MSI Architectures: x86 arm arm64 Type: vm ioctl Parameters: struct kvm_msi (in) Returns: >0 on delivery, 0 if guest blocked the MSI, and -1 on error Directly inject a MSI message. Only valid with in-kernel irqchip that handles MSI messages. struct kvm_msi { __u32 address_lo; __u32 address_hi; __u32 data; __u32 flags; __u32 devid; __u8 pad[12]; }; flags: KVM_MSI_VALID_DEVID: devid contains a valid value. The per-VM KVM_CAP_MSI_DEVID capability advertises the requirement to provide the device ID. If this capability is not available, userspace should never set the KVM_MSI_VALID_DEVID flag as the ioctl might fail. If KVM_MSI_VALID_DEVID is set, devid contains a unique device identifier for the device that wrote the MSI message. For PCI, this is usually a BFD identifier in the lower 16 bits. On x86, address_hi is ignored unless the KVM_X2APIC_API_USE_32BIT_IDS feature of KVM_CAP_X2APIC_API capability is enabled. If it is enabled, address_hi bits 31-8 provide bits 31-8 of the destination id. Bits 7-0 of address_hi must be zero. 4.71 KVM_CREATE_PIT2 Capability: KVM_CAP_PIT2 Architectures: x86 Type: vm ioctl Parameters: struct kvm_pit_config (in) Returns: 0 on success, -1 on error Creates an in-kernel device model for the i8254 PIT. This call is only valid after enabling in-kernel irqchip support via KVM_CREATE_IRQCHIP. The following parameters have to be passed: struct kvm_pit_config { __u32 flags; __u32 pad[15]; }; Valid flags are: #define KVM_PIT_SPEAKER_DUMMY 1 /* emulate speaker port stub */ PIT timer interrupts may use a per-VM kernel thread for injection. If it exists, this thread will have a name of the following pattern: kvm-pit/ When running a guest with elevated priorities, the scheduling parameters of this thread may have to be adjusted accordingly. This IOCTL replaces the obsolete KVM_CREATE_PIT. 4.72 KVM_GET_PIT2 Capability: KVM_CAP_PIT_STATE2 Architectures: x86 Type: vm ioctl Parameters: struct kvm_pit_state2 (out) Returns: 0 on success, -1 on error Retrieves the state of the in-kernel PIT model. Only valid after KVM_CREATE_PIT2. The state is returned in the following structure: struct kvm_pit_state2 { struct kvm_pit_channel_state channels[3]; __u32 flags; __u32 reserved[9]; }; Valid flags are: /* disable PIT in HPET legacy mode */ #define KVM_PIT_FLAGS_HPET_LEGACY 0x00000001 This IOCTL replaces the obsolete KVM_GET_PIT. 4.73 KVM_SET_PIT2 Capability: KVM_CAP_PIT_STATE2 Architectures: x86 Type: vm ioctl Parameters: struct kvm_pit_state2 (in) Returns: 0 on success, -1 on error Sets the state of the in-kernel PIT model. Only valid after KVM_CREATE_PIT2. See KVM_GET_PIT2 for details on struct kvm_pit_state2. This IOCTL replaces the obsolete KVM_SET_PIT. 4.74 KVM_PPC_GET_SMMU_INFO Capability: KVM_CAP_PPC_GET_SMMU_INFO Architectures: powerpc Type: vm ioctl Parameters: None Returns: 0 on success, -1 on error This populates and returns a structure describing the features of the "Server" class MMU emulation supported by KVM. This can in turn be used by userspace to generate the appropriate device-tree properties for the guest operating system. The structure contains some global information, followed by an array of supported segment page sizes: struct kvm_ppc_smmu_info { __u64 flags; __u32 slb_size; __u32 pad; struct kvm_ppc_one_seg_page_size sps[KVM_PPC_PAGE_SIZES_MAX_SZ]; }; The supported flags are: - KVM_PPC_PAGE_SIZES_REAL: When that flag is set, guest page sizes must "fit" the backing store page sizes. When not set, any page size in the list can be used regardless of how they are backed by userspace. - KVM_PPC_1T_SEGMENTS The emulated MMU supports 1T segments in addition to the standard 256M ones. The "slb_size" field indicates how many SLB entries are supported The "sps" array contains 8 entries indicating the supported base page sizes for a segment in increasing order. Each entry is defined as follow: struct kvm_ppc_one_seg_page_size { __u32 page_shift; /* Base page shift of segment (or 0) */ __u32 slb_enc; /* SLB encoding for BookS */ struct kvm_ppc_one_page_size enc[KVM_PPC_PAGE_SIZES_MAX_SZ]; }; An entry with a "page_shift" of 0 is unused. Because the array is organized in increasing order, a lookup can stop when encoutering such an entry. The "slb_enc" field provides the encoding to use in the SLB for the page size. The bits are in positions such as the value can directly be OR'ed into the "vsid" argument of the slbmte instruction. The "enc" array is a list which for each of those segment base page size provides the list of supported actual page sizes (which can be only larger or equal to the base page size), along with the corresponding encoding in the hash PTE. Similarly, the array is 8 entries sorted by increasing sizes and an entry with a "0" shift is an empty entry and a terminator: struct kvm_ppc_one_page_size { __u32 page_shift; /* Page shift (or 0) */ __u32 pte_enc; /* Encoding in the HPTE (>>12) */ }; The "pte_enc" field provides a value that can OR'ed into the hash PTE's RPN field (ie, it needs to be shifted left by 12 to OR it into the hash PTE second double word). 4.75 KVM_IRQFD Capability: KVM_CAP_IRQFD Architectures: x86 s390 arm arm64 Type: vm ioctl Parameters: struct kvm_irqfd (in) Returns: 0 on success, -1 on error Allows setting an eventfd to directly trigger a guest interrupt. kvm_irqfd.fd specifies the file descriptor to use as the eventfd and kvm_irqfd.gsi specifies the irqchip pin toggled by this event. When an event is triggered on the eventfd, an interrupt is injected into the guest using the specified gsi pin. The irqfd is removed using the KVM_IRQFD_FLAG_DEASSIGN flag, specifying both kvm_irqfd.fd and kvm_irqfd.gsi. With KVM_CAP_IRQFD_RESAMPLE, KVM_IRQFD supports a de-assert and notify mechanism allowing emulation of level-triggered, irqfd-based interrupts. When KVM_IRQFD_FLAG_RESAMPLE is set the user must pass an additional eventfd in the kvm_irqfd.resamplefd field. When operating in resample mode, posting of an interrupt through kvm_irq.fd asserts the specified gsi in the irqchip. When the irqchip is resampled, such as from an EOI, the gsi is de-asserted and the user is notified via kvm_irqfd.resamplefd. It is the user's responsibility to re-queue the interrupt if the device making use of it still requires service. Note that closing the resamplefd is not sufficient to disable the irqfd. The KVM_IRQFD_FLAG_RESAMPLE is only necessary on assignment and need not be specified with KVM_IRQFD_FLAG_DEASSIGN. On arm/arm64, gsi routing being supported, the following can happen: - in case no routing entry is associated to this gsi, injection fails - in case the gsi is associated to an irqchip routing entry, irqchip.pin + 32 corresponds to the injected SPI ID. - in case the gsi is associated to an MSI routing entry, the MSI message and device ID are translated into an LPI (support restricted to GICv3 ITS in-kernel emulation). 4.76 KVM_PPC_ALLOCATE_HTAB Capability: KVM_CAP_PPC_ALLOC_HTAB Architectures: powerpc Type: vm ioctl Parameters: Pointer to u32 containing hash table order (in/out) Returns: 0 on success, -1 on error This requests the host kernel to allocate an MMU hash table for a guest using the PAPR paravirtualization interface. This only does anything if the kernel is configured to use the Book 3S HV style of virtualization. Otherwise the capability doesn't exist and the ioctl returns an ENOTTY error. The rest of this description assumes Book 3S HV. There must be no vcpus running when this ioctl is called; if there are, it will do nothing and return an EBUSY error. The parameter is a pointer to a 32-bit unsigned integer variable containing the order (log base 2) of the desired size of the hash table, which must be between 18 and 46. On successful return from the ioctl, the value will not be changed by the kernel. If no hash table has been allocated when any vcpu is asked to run (with the KVM_RUN ioctl), the host kernel will allocate a default-sized hash table (16 MB). If this ioctl is called when a hash table has already been allocated, with a different order from the existing hash table, the existing hash table will be freed and a new one allocated. If this is ioctl is called when a hash table has already been allocated of the same order as specified, the kernel will clear out the existing hash table (zero all HPTEs). In either case, if the guest is using the virtualized real-mode area (VRMA) facility, the kernel will re-create the VMRA HPTEs on the next KVM_RUN of any vcpu. 4.77 KVM_S390_INTERRUPT Capability: basic Architectures: s390 Type: vm ioctl, vcpu ioctl Parameters: struct kvm_s390_interrupt (in) Returns: 0 on success, -1 on error Allows to inject an interrupt to the guest. Interrupts can be floating (vm ioctl) or per cpu (vcpu ioctl), depending on the interrupt type. Interrupt parameters are passed via kvm_s390_interrupt: struct kvm_s390_interrupt { __u32 type; __u32 parm; __u64 parm64; }; type can be one of the following: KVM_S390_SIGP_STOP (vcpu) - sigp stop; optional flags in parm KVM_S390_PROGRAM_INT (vcpu) - program check; code in parm KVM_S390_SIGP_SET_PREFIX (vcpu) - sigp set prefix; prefix address in parm KVM_S390_RESTART (vcpu) - restart KVM_S390_INT_CLOCK_COMP (vcpu) - clock comparator interrupt KVM_S390_INT_CPU_TIMER (vcpu) - CPU timer interrupt KVM_S390_INT_VIRTIO (vm) - virtio external interrupt; external interrupt parameters in parm and parm64 KVM_S390_INT_SERVICE (vm) - sclp external interrupt; sclp parameter in parm KVM_S390_INT_EMERGENCY (vcpu) - sigp emergency; source cpu in parm KVM_S390_INT_EXTERNAL_CALL (vcpu) - sigp external call; source cpu in parm KVM_S390_INT_IO(ai,cssid,ssid,schid) (vm) - compound value to indicate an I/O interrupt (ai - adapter interrupt; cssid,ssid,schid - subchannel); I/O interruption parameters in parm (subchannel) and parm64 (intparm, interruption subclass) KVM_S390_MCHK (vm, vcpu) - machine check interrupt; cr 14 bits in parm, machine check interrupt code in parm64 (note that machine checks needing further payload are not supported by this ioctl) Note that the vcpu ioctl is asynchronous to vcpu execution. 4.78 KVM_PPC_GET_HTAB_FD Capability: KVM_CAP_PPC_HTAB_FD Architectures: powerpc Type: vm ioctl Parameters: Pointer to struct kvm_get_htab_fd (in) Returns: file descriptor number (>= 0) on success, -1 on error This returns a file descriptor that can be used either to read out the entries in the guest's hashed page table (HPT), or to write entries to initialize the HPT. The returned fd can only be written to if the KVM_GET_HTAB_WRITE bit is set in the flags field of the argument, and can only be read if that bit is clear. The argument struct looks like this: /* For KVM_PPC_GET_HTAB_FD */ struct kvm_get_htab_fd { __u64 flags; __u64 start_index; __u64 reserved[2]; }; /* Values for kvm_get_htab_fd.flags */ #define KVM_GET_HTAB_BOLTED_ONLY ((__u64)0x1) #define KVM_GET_HTAB_WRITE ((__u64)0x2) The `start_index' field gives the index in the HPT of the entry at which to start reading. It is ignored when writing. Reads on the fd will initially supply information about all "interesting" HPT entries. Interesting entries are those with the bolted bit set, if the KVM_GET_HTAB_BOLTED_ONLY bit is set, otherwise all entries. When the end of the HPT is reached, the read() will return. If read() is called again on the fd, it will start again from the beginning of the HPT, but will only return HPT entries that have changed since they were last read. Data read or written is structured as a header (8 bytes) followed by a series of valid HPT entries (16 bytes) each. The header indicates how many valid HPT entries there are and how many invalid entries follow the valid entries. The invalid entries are not represented explicitly in the stream. The header format is: struct kvm_get_htab_header { __u32 index; __u16 n_valid; __u16 n_invalid; }; Writes to the fd create HPT entries starting at the index given in the header; first `n_valid' valid entries with contents from the data written, then `n_invalid' invalid entries, invalidating any previously valid entries found. 4.79 KVM_CREATE_DEVICE Capability: KVM_CAP_DEVICE_CTRL Type: vm ioctl Parameters: struct kvm_create_device (in/out) Returns: 0 on success, -1 on error Errors: ENODEV: The device type is unknown or unsupported EEXIST: Device already created, and this type of device may not be instantiated multiple times Other error conditions may be defined by individual device types or have their standard meanings. Creates an emulated device in the kernel. The file descriptor returned in fd can be used with KVM_SET/GET/HAS_DEVICE_ATTR. If the KVM_CREATE_DEVICE_TEST flag is set, only test whether the device type is supported (not necessarily whether it can be created in the current vm). Individual devices should not define flags. Attributes should be used for specifying any behavior that is not implied by the device type number. struct kvm_create_device { __u32 type; /* in: KVM_DEV_TYPE_xxx */ __u32 fd; /* out: device handle */ __u32 flags; /* in: KVM_CREATE_DEVICE_xxx */ }; 4.80 KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device, KVM_CAP_VCPU_ATTRIBUTES for vcpu device Type: device ioctl, vm ioctl, vcpu ioctl Parameters: struct kvm_device_attr Returns: 0 on success, -1 on error Errors: ENXIO: The group or attribute is unknown/unsupported for this device or hardware support is missing. EPERM: The attribute cannot (currently) be accessed this way (e.g. read-only attribute, or attribute that only makes sense when the device is in a different state) Other error conditions may be defined by individual device types. Gets/sets a specified piece of device configuration and/or state. The semantics are device-specific. See individual device documentation in the "devices" directory. As with ONE_REG, the size of the data transferred is defined by the particular attribute. struct kvm_device_attr { __u32 flags; /* no flags currently defined */ __u32 group; /* device-defined */ __u64 attr; /* group-defined */ __u64 addr; /* userspace address of attr data */ }; 4.81 KVM_HAS_DEVICE_ATTR Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device, KVM_CAP_VCPU_ATTRIBUTES for vcpu device Type: device ioctl, vm ioctl, vcpu ioctl Parameters: struct kvm_device_attr Returns: 0 on success, -1 on error Errors: ENXIO: The group or attribute is unknown/unsupported for this device or hardware support is missing. Tests whether a device supports a particular attribute. A successful return indicates the attribute is implemented. It does not necessarily indicate that the attribute can be read or written in the device's current state. "addr" is ignored. 4.82 KVM_ARM_VCPU_INIT Capability: basic Architectures: arm, arm64 Type: vcpu ioctl Parameters: struct kvm_vcpu_init (in) Returns: 0 on success; -1 on error Errors:  EINVAL:    the target is unknown, or the combination of features is invalid.  ENOENT:    a features bit specified is unknown. This tells KVM what type of CPU to present to the guest, and what optional features it should have.  This will cause a reset of the cpu registers to their initial values.  If this is not called, KVM_RUN will return ENOEXEC for that vcpu. Note that because some registers reflect machine topology, all vcpus should be created before this ioctl is invoked. Userspace can call this function multiple times for a given vcpu, including after the vcpu has been run. This will reset the vcpu to its initial state. All calls to this function after the initial call must use the same target and same set of feature flags, otherwise EINVAL will be returned. Possible features: - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state. Depends on KVM_CAP_ARM_PSCI. If not set, the CPU will be powered on and execute guest code when KVM_RUN is called. - KVM_ARM_VCPU_EL1_32BIT: Starts the CPU in a 32bit mode. Depends on KVM_CAP_ARM_EL1_32BIT (arm64 only). - KVM_ARM_VCPU_PSCI_0_2: Emulate PSCI v0.2 for the CPU. Depends on KVM_CAP_ARM_PSCI_0_2. - KVM_ARM_VCPU_PMU_V3: Emulate PMUv3 for the CPU. Depends on KVM_CAP_ARM_PMU_V3. 4.83 KVM_ARM_PREFERRED_TARGET Capability: basic Architectures: arm, arm64 Type: vm ioctl Parameters: struct struct kvm_vcpu_init (out) Returns: 0 on success; -1 on error Errors: ENODEV: no preferred target available for the host This queries KVM for preferred CPU target type which can be emulated by KVM on underlying host. The ioctl returns struct kvm_vcpu_init instance containing information about preferred CPU target type and recommended features for it. The kvm_vcpu_init->features bitmap returned will have feature bits set if the preferred target recommends setting these features, but this is not mandatory. The information returned by this ioctl can be used to prepare an instance of struct kvm_vcpu_init for KVM_ARM_VCPU_INIT ioctl which will result in in VCPU matching underlying host. 4.84 KVM_GET_REG_LIST Capability: basic Architectures: arm, arm64, mips Type: vcpu ioctl Parameters: struct kvm_reg_list (in/out) Returns: 0 on success; -1 on error Errors:  E2BIG:     the reg index list is too big to fit in the array specified by             the user (the number required will be written into n). struct kvm_reg_list { __u64 n; /* number of registers in reg[] */ __u64 reg[0]; }; This ioctl returns the guest registers that are supported for the KVM_GET_ONE_REG/KVM_SET_ONE_REG calls. 4.85 KVM_ARM_SET_DEVICE_ADDR (deprecated) Capability: KVM_CAP_ARM_SET_DEVICE_ADDR Architectures: arm, arm64 Type: vm ioctl Parameters: struct kvm_arm_device_address (in) Returns: 0 on success, -1 on error Errors: ENODEV: The device id is unknown ENXIO: Device not supported on current system EEXIST: Address already set E2BIG: Address outside guest physical address space EBUSY: Address overlaps with other device range struct kvm_arm_device_addr { __u64 id; __u64 addr; }; Specify a device address in the guest's physical address space where guests can access emulated or directly exposed devices, which the host kernel needs to know about. The id field is an architecture specific identifier for a specific device. ARM/arm64 divides the id field into two parts, a device id and an address type id specific to the individual device.  bits: | 63 ... 32 | 31 ... 16 | 15 ... 0 | field: | 0x00000000 | device id | addr type id | ARM/arm64 currently only require this when using the in-kernel GIC support for the hardware VGIC features, using KVM_ARM_DEVICE_VGIC_V2 as the device id. When setting the base address for the guest's mapping of the VGIC virtual CPU and distributor interface, the ioctl must be called after calling KVM_CREATE_IRQCHIP, but before calling KVM_RUN on any of the VCPUs. Calling this ioctl twice for any of the base addresses will return -EEXIST. Note, this IOCTL is deprecated and the more flexible SET/GET_DEVICE_ATTR API should be used instead. 4.86 KVM_PPC_RTAS_DEFINE_TOKEN Capability: KVM_CAP_PPC_RTAS Architectures: ppc Type: vm ioctl Parameters: struct kvm_rtas_token_args Returns: 0 on success, -1 on error Defines a token value for a RTAS (Run Time Abstraction Services) service in order to allow it to be handled in the kernel. The argument struct gives the name of the service, which must be the name of a service that has a kernel-side implementation. If the token value is non-zero, it will be associated with that service, and subsequent RTAS calls by the guest specifying that token will be handled by the kernel. If the token value is 0, then any token associated with the service will be forgotten, and subsequent RTAS calls by the guest for that service will be passed to userspace to be handled. 4.87 KVM_SET_GUEST_DEBUG Capability: KVM_CAP_SET_GUEST_DEBUG Architectures: x86, s390, ppc, arm64 Type: vcpu ioctl Parameters: struct kvm_guest_debug (in) Returns: 0 on success; -1 on error struct kvm_guest_debug { __u32 control; __u32 pad; struct kvm_guest_debug_arch arch; }; Set up the processor specific debug registers and configure vcpu for handling guest debug events. There are two parts to the structure, the first a control bitfield indicates the type of debug events to handle when running. Common control bits are: - KVM_GUESTDBG_ENABLE: guest debugging is enabled - KVM_GUESTDBG_SINGLESTEP: the next run should single-step The top 16 bits of the control field are architecture specific control flags which can include the following: - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64] - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390, arm64] - KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86] - KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86] - KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390] For example KVM_GUESTDBG_USE_SW_BP indicates that software breakpoints are enabled in memory so we need to ensure breakpoint exceptions are correctly trapped and the KVM run loop exits at the breakpoint and not running off into the normal guest vector. For KVM_GUESTDBG_USE_HW_BP we need to ensure the guest vCPUs architecture specific registers are updated to the correct (supplied) values. The second part of the structure is architecture specific and typically contains a set of debug registers. For arm64 the number of debug registers is implementation defined and can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive number indicating the number of supported registers. When debug events exit the main run loop with the reason KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run structure containing architecture specific debug information. 4.88 KVM_GET_EMULATED_CPUID Capability: KVM_CAP_EXT_EMUL_CPUID Architectures: x86 Type: system ioctl Parameters: struct kvm_cpuid2 (in/out) Returns: 0 on success, -1 on error struct kvm_cpuid2 { __u32 nent; __u32 flags; struct kvm_cpuid_entry2 entries[0]; }; The member 'flags' is used for passing flags from userspace. #define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0) #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1) #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2) struct kvm_cpuid_entry2 { __u32 function; __u32 index; __u32 flags; __u32 eax; __u32 ebx; __u32 ecx; __u32 edx; __u32 padding[3]; }; This ioctl returns x86 cpuid features which are emulated by kvm.Userspace can use the information returned by this ioctl to query which features are emulated by kvm instead of being present natively. Userspace invokes KVM_GET_EMULATED_CPUID by passing a kvm_cpuid2 structure with the 'nent' field indicating the number of entries in the variable-size array 'entries'. If the number of entries is too low to describe the cpu capabilities, an error (E2BIG) is returned. If the number is too high, the 'nent' field is adjusted and an error (ENOMEM) is returned. If the number is just right, the 'nent' field is adjusted to the number of valid entries in the 'entries' array, which is then filled. The entries returned are the set CPUID bits of the respective features which kvm emulates, as returned by the CPUID instruction, with unknown or unsupported feature bits cleared. Features like x2apic, for example, may not be present in the host cpu but are exposed by kvm in KVM_GET_SUPPORTED_CPUID because they can be emulated efficiently and thus not included here. The fields in each entry are defined as follows: function: the eax value used to obtain the entry index: the ecx value used to obtain the entry (for entries that are affected by ecx) flags: an OR of zero or more of the following: KVM_CPUID_FLAG_SIGNIFCANT_INDEX: if the index field is valid KVM_CPUID_FLAG_STATEFUL_FUNC: if cpuid for this function returns different values for successive invocations; there will be several entries with the same function, all with this flag set KVM_CPUID_FLAG_STATE_READ_NEXT: for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is the first entry to be read by a cpu eax, ebx, ecx, edx: the values returned by the cpuid instruction for this function/index combination 4.89 KVM_S390_MEM_OP Capability: KVM_CAP_S390_MEM_OP Architectures: s390 Type: vcpu ioctl Parameters: struct kvm_s390_mem_op (in) Returns: = 0 on success, < 0 on generic error (e.g. -EFAULT or -ENOMEM), > 0 if an exception occurred while walking the page tables Read or write data from/to the logical (virtual) memory of a VCPU. Parameters are specified via the following structure: struct kvm_s390_mem_op { __u64 gaddr; /* the guest address */ __u64 flags; /* flags */ __u32 size; /* amount of bytes */ __u32 op; /* type of operation */ __u64 buf; /* buffer in userspace */ __u8 ar; /* the access register number */ __u8 reserved[31]; /* should be set to 0 */ }; The type of operation is specified in the "op" field. It is either KVM_S390_MEMOP_LOGICAL_READ for reading from logical memory space or KVM_S390_MEMOP_LOGICAL_WRITE for writing to logical memory space. The KVM_S390_MEMOP_F_CHECK_ONLY flag can be set in the "flags" field to check whether the corresponding memory access would create an access exception (without touching the data in the memory at the destination). In case an access exception occurred while walking the MMU tables of the guest, the ioctl returns a positive error number to indicate the type of exception. This exception is also raised directly at the corresponding VCPU if the flag KVM_S390_MEMOP_F_INJECT_EXCEPTION is set in the "flags" field. The start address of the memory region has to be specified in the "gaddr" field, and the length of the region in the "size" field. "buf" is the buffer supplied by the userspace application where the read data should be written to for KVM_S390_MEMOP_LOGICAL_READ, or where the data that should be written is stored for a KVM_S390_MEMOP_LOGICAL_WRITE. "buf" is unused and can be NULL when KVM_S390_MEMOP_F_CHECK_ONLY is specified. "ar" designates the access register number to be used. The "reserved" field is meant for future extensions. It is not used by KVM with the currently defined set of flags. 4.90 KVM_S390_GET_SKEYS Capability: KVM_CAP_S390_SKEYS Architectures: s390 Type: vm ioctl Parameters: struct kvm_s390_skeys Returns: 0 on success, KVM_S390_GET_KEYS_NONE if guest is not using storage keys, negative value on error This ioctl is used to get guest storage key values on the s390 architecture. The ioctl takes parameters via the kvm_s390_skeys struct. struct kvm_s390_skeys { __u64 start_gfn; __u64 count; __u64 skeydata_addr; __u32 flags; __u32 reserved[9]; }; The start_gfn field is the number of the first guest frame whose storage keys you want to get. The count field is the number of consecutive frames (starting from start_gfn) whose storage keys to get. The count field must be at least 1 and the maximum allowed value is defined as KVM_S390_SKEYS_ALLOC_MAX. Values outside this range will cause the ioctl to return -EINVAL. The skeydata_addr field is the address to a buffer large enough to hold count bytes. This buffer will be filled with storage key data by the ioctl. 4.91 KVM_S390_SET_SKEYS Capability: KVM_CAP_S390_SKEYS Architectures: s390 Type: vm ioctl Parameters: struct kvm_s390_skeys Returns: 0 on success, negative value on error This ioctl is used to set guest storage key values on the s390 architecture. The ioctl takes parameters via the kvm_s390_skeys struct. See section on KVM_S390_GET_SKEYS for struct definition. The start_gfn field is the number of the first guest frame whose storage keys you want to set. The count field is the number of consecutive frames (starting from start_gfn) whose storage keys to get. The count field must be at least 1 and the maximum allowed value is defined as KVM_S390_SKEYS_ALLOC_MAX. Values outside this range will cause the ioctl to return -EINVAL. The skeydata_addr field is the address to a buffer containing count bytes of storage keys. Each byte in the buffer will be set as the storage key for a single frame starting at start_gfn for count frames. Note: If any architecturally invalid key value is found in the given data then the ioctl will return -EINVAL. 4.92 KVM_S390_IRQ Capability: KVM_CAP_S390_INJECT_IRQ Architectures: s390 Type: vcpu ioctl Parameters: struct kvm_s390_irq (in) Returns: 0 on success, -1 on error Errors: EINVAL: interrupt type is invalid type is KVM_S390_SIGP_STOP and flag parameter is invalid value type is KVM_S390_INT_EXTERNAL_CALL and code is bigger than the maximum of VCPUs EBUSY: type is KVM_S390_SIGP_SET_PREFIX and vcpu is not stopped type is KVM_S390_SIGP_STOP and a stop irq is already pending type is KVM_S390_INT_EXTERNAL_CALL and an external call interrupt is already pending Allows to inject an interrupt to the guest. Using struct kvm_s390_irq as a parameter allows to inject additional payload which is not possible via KVM_S390_INTERRUPT. Interrupt parameters are passed via kvm_s390_irq: struct kvm_s390_irq { __u64 type; union { struct kvm_s390_io_info io; struct kvm_s390_ext_info ext; struct kvm_s390_pgm_info pgm; struct kvm_s390_emerg_info emerg; struct kvm_s390_extcall_info extcall; struct kvm_s390_prefix_info prefix; struct kvm_s390_stop_info stop; struct kvm_s390_mchk_info mchk; char reserved[64]; } u; }; type can be one of the following: KVM_S390_SIGP_STOP - sigp stop; parameter in .stop KVM_S390_PROGRAM_INT - program check; parameters in .pgm KVM_S390_SIGP_SET_PREFIX - sigp set prefix; parameters in .prefix KVM_S390_RESTART - restart; no parameters KVM_S390_INT_CLOCK_COMP - clock comparator interrupt; no parameters KVM_S390_INT_CPU_TIMER - CPU timer interrupt; no parameters KVM_S390_INT_EMERGENCY - sigp emergency; parameters in .emerg KVM_S390_INT_EXTERNAL_CALL - sigp external call; parameters in .extcall KVM_S390_MCHK - machine check interrupt; parameters in .mchk Note that the vcpu ioctl is asynchronous to vcpu execution. 4.94 KVM_S390_GET_IRQ_STATE Capability: KVM_CAP_S390_IRQ_STATE Architectures: s390 Type: vcpu ioctl Parameters: struct kvm_s390_irq_state (out) Returns: >= number of bytes copied into buffer, -EINVAL if buffer size is 0, -ENOBUFS if buffer size is too small to fit all pending interrupts, -EFAULT if the buffer address was invalid This ioctl allows userspace to retrieve the complete state of all currently pending interrupts in a single buffer. Use cases include migration and introspection. The parameter structure contains the address of a userspace buffer and its length: struct kvm_s390_irq_state { __u64 buf; __u32 flags; /* will stay unused for compatibility reasons */ __u32 len; __u32 reserved[4]; /* will stay unused for compatibility reasons */ }; Userspace passes in the above struct and for each pending interrupt a struct kvm_s390_irq is copied to the provided buffer. The structure contains a flags and a reserved field for future extensions. As the kernel never checked for flags == 0 and QEMU never pre-zeroed flags and reserved, these fields can not be used in the future without breaking compatibility. If -ENOBUFS is returned the buffer provided was too small and userspace may retry with a bigger buffer. 4.95 KVM_S390_SET_IRQ_STATE Capability: KVM_CAP_S390_IRQ_STATE Architectures: s390 Type: vcpu ioctl Parameters: struct kvm_s390_irq_state (in) Returns: 0 on success, -EFAULT if the buffer address was invalid, -EINVAL for an invalid buffer length (see below), -EBUSY if there were already interrupts pending, errors occurring when actually injecting the interrupt. See KVM_S390_IRQ. This ioctl allows userspace to set the complete state of all cpu-local interrupts currently pending for the vcpu. It is intended for restoring interrupt state after a migration. The input parameter is a userspace buffer containing a struct kvm_s390_irq_state: struct kvm_s390_irq_state { __u64 buf; __u32 flags; /* will stay unused for compatibility reasons */ __u32 len; __u32 reserved[4]; /* will stay unused for compatibility reasons */ }; The restrictions for flags and reserved apply as well. (see KVM_S390_GET_IRQ_STATE) The userspace memory referenced by buf contains a struct kvm_s390_irq for each interrupt to be injected into the guest. If one of the interrupts could not be injected for some reason the ioctl aborts. len must be a multiple of sizeof(struct kvm_s390_irq). It must be > 0 and it must not exceed (max_vcpus + 32) * sizeof(struct kvm_s390_irq), which is the maximum number of possibly pending cpu-local interrupts. 4.96 KVM_SMI Capability: KVM_CAP_X86_SMM Architectures: x86 Type: vcpu ioctl Parameters: none Returns: 0 on success, -1 on error Queues an SMI on the thread's vcpu. 4.97 KVM_CAP_PPC_MULTITCE Capability: KVM_CAP_PPC_MULTITCE Architectures: ppc Type: vm This capability means the kernel is capable of handling hypercalls H_PUT_TCE_INDIRECT and H_STUFF_TCE without passing those into the user space. This significantly accelerates DMA operations for PPC KVM guests. User space should expect that its handlers for these hypercalls are not going to be called if user space previously registered LIOBN in KVM (via KVM_CREATE_SPAPR_TCE or similar calls). In order to enable H_PUT_TCE_INDIRECT and H_STUFF_TCE use in the guest, user space might have to advertise it for the guest. For example, IBM pSeries (sPAPR) guest starts using them if "hcall-multi-tce" is present in the "ibm,hypertas-functions" device-tree property. The hypercalls mentioned above may or may not be processed successfully in the kernel based fast path. If they can not be handled by the kernel, they will get passed on to user space. So user space still has to have an implementation for these despite the in kernel acceleration. This capability is always enabled. 4.98 KVM_CREATE_SPAPR_TCE_64 Capability: KVM_CAP_SPAPR_TCE_64 Architectures: powerpc Type: vm ioctl Parameters: struct kvm_create_spapr_tce_64 (in) Returns: file descriptor for manipulating the created TCE table This is an extension for KVM_CAP_SPAPR_TCE which only supports 32bit windows, described in 4.62 KVM_CREATE_SPAPR_TCE This capability uses extended struct in ioctl interface: /* for KVM_CAP_SPAPR_TCE_64 */ struct kvm_create_spapr_tce_64 { __u64 liobn; __u32 page_shift; __u32 flags; __u64 offset; /* in pages */ __u64 size; /* in pages */ }; The aim of extension is to support an additional bigger DMA window with a variable page size. KVM_CREATE_SPAPR_TCE_64 receives a 64bit window size, an IOMMU page shift and a bus offset of the corresponding DMA window, @size and @offset are numbers of IOMMU pages. @flags are not used at the moment. The rest of functionality is identical to KVM_CREATE_SPAPR_TCE. 4.99 KVM_REINJECT_CONTROL Capability: KVM_CAP_REINJECT_CONTROL Architectures: x86 Type: vm ioctl Parameters: struct kvm_reinject_control (in) Returns: 0 on success, -EFAULT if struct kvm_reinject_control cannot be read, -ENXIO if KVM_CREATE_PIT or KVM_CREATE_PIT2 didn't succeed earlier. i8254 (PIT) has two modes, reinject and !reinject. The default is reinject, where KVM queues elapsed i8254 ticks and monitors completion of interrupt from vector(s) that i8254 injects. Reinject mode dequeues a tick and injects its interrupt whenever there isn't a pending interrupt from i8254. !reinject mode injects an interrupt as soon as a tick arrives. struct kvm_reinject_control { __u8 pit_reinject; __u8 reserved[31]; }; pit_reinject = 0 (!reinject mode) is recommended, unless running an old operating system that uses the PIT for timing (e.g. Linux 2.4.x). 4.100 KVM_PPC_CONFIGURE_V3_MMU Capability: KVM_CAP_PPC_RADIX_MMU or KVM_CAP_PPC_HASH_MMU_V3 Architectures: ppc Type: vm ioctl Parameters: struct kvm_ppc_mmuv3_cfg (in) Returns: 0 on success, -EFAULT if struct kvm_ppc_mmuv3_cfg cannot be read, -EINVAL if the configuration is invalid This ioctl controls whether the guest will use radix or HPT (hashed page table) translation, and sets the pointer to the process table for the guest. struct kvm_ppc_mmuv3_cfg { __u64 flags; __u64 process_table; }; There are two bits that can be set in flags; KVM_PPC_MMUV3_RADIX and KVM_PPC_MMUV3_GTSE. KVM_PPC_MMUV3_RADIX, if set, configures the guest to use radix tree translation, and if clear, to use HPT translation. KVM_PPC_MMUV3_GTSE, if set and if KVM permits it, configures the guest to be able to use the global TLB and SLB invalidation instructions; if clear, the guest may not use these instructions. The process_table field specifies the address and size of the guest process table, which is in the guest's space. This field is formatted as the second doubleword of the partition table entry, as defined in the Power ISA V3.00, Book III section 5.7.6.1. 4.101 KVM_PPC_GET_RMMU_INFO Capability: KVM_CAP_PPC_RADIX_MMU Architectures: ppc Type: vm ioctl Parameters: struct kvm_ppc_rmmu_info (out) Returns: 0 on success, -EFAULT if struct kvm_ppc_rmmu_info cannot be written, -EINVAL if no useful information can be returned This ioctl returns a structure containing two things: (a) a list containing supported radix tree geometries, and (b) a list that maps page sizes to put in the "AP" (actual page size) field for the tlbie (TLB invalidate entry) instruction. struct kvm_ppc_rmmu_info { struct kvm_ppc_radix_geom { __u8 page_shift; __u8 level_bits[4]; __u8 pad[3]; } geometries[8]; __u32 ap_encodings[8]; }; The geometries[] field gives up to 8 supported geometries for the radix page table, in terms of the log base 2 of the smallest page size, and the number of bits indexed at each level of the tree, from the PTE level up to the PGD level in that order. Any unused entries will have 0 in the page_shift field. The ap_encodings gives the supported page sizes and their AP field encodings, encoded with the AP value in the top 3 bits and the log base 2 of the page size in the bottom 6 bits. 4.102 KVM_PPC_RESIZE_HPT_PREPARE Capability: KVM_CAP_SPAPR_RESIZE_HPT Architectures: powerpc Type: vm ioctl Parameters: struct kvm_ppc_resize_hpt (in) Returns: 0 on successful completion, >0 if a new HPT is being prepared, the value is an estimated number of milliseconds until preparation is complete -EFAULT if struct kvm_reinject_control cannot be read, -EINVAL if the supplied shift or flags are invalid -ENOMEM if unable to allocate the new HPT -ENOSPC if there was a hash collision when moving existing HPT entries to the new HPT -EIO on other error conditions Used to implement the PAPR extension for runtime resizing of a guest's Hashed Page Table (HPT). Specifically this starts, stops or monitors the preparation of a new potential HPT for the guest, essentially implementing the H_RESIZE_HPT_PREPARE hypercall. If called with shift > 0 when there is no pending HPT for the guest, this begins preparation of a new pending HPT of size 2^(shift) bytes. It then returns a positive integer with the estimated number of milliseconds until preparation is complete. If called when there is a pending HPT whose size does not match that requested in the parameters, discards the existing pending HPT and creates a new one as above. If called when there is a pending HPT of the size requested, will: * If preparation of the pending HPT is already complete, return 0 * If preparation of the pending HPT has failed, return an error code, then discard the pending HPT. * If preparation of the pending HPT is still in progress, return an estimated number of milliseconds until preparation is complete. If called with shift == 0, discards any currently pending HPT and returns 0 (i.e. cancels any in-progress preparation). flags is reserved for future expansion, currently setting any bits in flags will result in an -EINVAL. Normally this will be called repeatedly with the same parameters until it returns <= 0. The first call will initiate preparation, subsequent ones will monitor preparation until it completes or fails. struct kvm_ppc_resize_hpt { __u64 flags; __u32 shift; __u32 pad; }; 4.103 KVM_PPC_RESIZE_HPT_COMMIT Capability: KVM_CAP_SPAPR_RESIZE_HPT Architectures: powerpc Type: vm ioctl Parameters: struct kvm_ppc_resize_hpt (in) Returns: 0 on successful completion, -EFAULT if struct kvm_reinject_control cannot be read, -EINVAL if the supplied shift or flags are invalid -ENXIO is there is no pending HPT, or the pending HPT doesn't have the requested size -EBUSY if the pending HPT is not fully prepared -ENOSPC if there was a hash collision when moving existing HPT entries to the new HPT -EIO on other error conditions Used to implement the PAPR extension for runtime resizing of a guest's Hashed Page Table (HPT). Specifically this requests that the guest be transferred to working with the new HPT, essentially implementing the H_RESIZE_HPT_COMMIT hypercall. This should only be called after KVM_PPC_RESIZE_HPT_PREPARE has returned 0 with the same parameters. In other cases KVM_PPC_RESIZE_HPT_COMMIT will return an error (usually -ENXIO or -EBUSY, though others may be possible if the preparation was started, but failed). This will have undefined effects on the guest if it has not already placed itself in a quiescent state where no vcpu will make MMU enabled memory accesses. On succsful completion, the pending HPT will become the guest's active HPT and the previous HPT will be discarded. On failure, the guest will still be operating on its previous HPT. struct kvm_ppc_resize_hpt { __u64 flags; __u32 shift; __u32 pad; }; 4.104 KVM_X86_GET_MCE_CAP_SUPPORTED Capability: KVM_CAP_MCE Architectures: x86 Type: system ioctl Parameters: u64 mce_cap (out) Returns: 0 on success, -1 on error Returns supported MCE capabilities. The u64 mce_cap parameter has the same format as the MSR_IA32_MCG_CAP register. Supported capabilities will have the corresponding bits set. 4.105 KVM_X86_SETUP_MCE Capability: KVM_CAP_MCE Architectures: x86 Type: vcpu ioctl Parameters: u64 mcg_cap (in) Returns: 0 on success, -EFAULT if u64 mcg_cap cannot be read, -EINVAL if the requested number of banks is invalid, -EINVAL if requested MCE capability is not supported. Initializes MCE support for use. The u64 mcg_cap parameter has the same format as the MSR_IA32_MCG_CAP register and specifies which capabilities should be enabled. The maximum supported number of error-reporting banks can be retrieved when checking for KVM_CAP_MCE. The supported capabilities can be retrieved with KVM_X86_GET_MCE_CAP_SUPPORTED. 4.106 KVM_X86_SET_MCE Capability: KVM_CAP_MCE Architectures: x86 Type: vcpu ioctl Parameters: struct kvm_x86_mce (in) Returns: 0 on success, -EFAULT if struct kvm_x86_mce cannot be read, -EINVAL if the bank number is invalid, -EINVAL if VAL bit is not set in status field. Inject a machine check error (MCE) into the guest. The input parameter is: struct kvm_x86_mce { __u64 status; __u64 addr; __u64 misc; __u64 mcg_status; __u8 bank; __u8 pad1[7]; __u64 pad2[3]; }; If the MCE being reported is an uncorrected error, KVM will inject it as an MCE exception into the guest. If the guest MCG_STATUS register reports that an MCE is in progress, KVM causes an KVM_EXIT_SHUTDOWN vmexit. Otherwise, if the MCE is a corrected error, KVM will just store it in the corresponding bank (provided this bank is not holding a previously reported uncorrected error). 4.107 KVM_S390_GET_CMMA_BITS Capability: KVM_CAP_S390_CMMA_MIGRATION Architectures: s390 Type: vm ioctl Parameters: struct kvm_s390_cmma_log (in, out) Returns: 0 on success, a negative value on error This ioctl is used to get the values of the CMMA bits on the s390 architecture. It is meant to be used in two scenarios: - During live migration to save the CMMA values. Live migration needs to be enabled via the KVM_REQ_START_MIGRATION VM property. - To non-destructively peek at the CMMA values, with the flag KVM_S390_CMMA_PEEK set. The ioctl takes parameters via the kvm_s390_cmma_log struct. The desired values are written to a buffer whose location is indicated via the "values" member in the kvm_s390_cmma_log struct. The values in the input struct are also updated as needed. Each CMMA value takes up one byte. struct kvm_s390_cmma_log { __u64 start_gfn; __u32 count; __u32 flags; union { __u64 remaining; __u64 mask; }; __u64 values; }; start_gfn is the number of the first guest frame whose CMMA values are to be retrieved, count is the length of the buffer in bytes, values points to the buffer where the result will be written to. If count is greater than KVM_S390_SKEYS_MAX, then it is considered to be KVM_S390_SKEYS_MAX. KVM_S390_SKEYS_MAX is re-used for consistency with other ioctls. The result is written in the buffer pointed to by the field values, and the values of the input parameter are updated as follows. Depending on the flags, different actions are performed. The only supported flag so far is KVM_S390_CMMA_PEEK. The default behaviour if KVM_S390_CMMA_PEEK is not set is: start_gfn will indicate the first page frame whose CMMA bits were dirty. It is not necessarily the same as the one passed as input, as clean pages are skipped. count will indicate the number of bytes actually written in the buffer. It can (and very often will) be smaller than the input value, since the buffer is only filled until 16 bytes of clean values are found (which are then not copied in the buffer). Since a CMMA migration block needs the base address and the length, for a total of 16 bytes, we will send back some clean data if there is some dirty data afterwards, as long as the size of the clean data does not exceed the size of the header. This allows to minimize the amount of data to be saved or transferred over the network at the expense of more roundtrips to userspace. The next invocation of the ioctl will skip over all the clean values, saving potentially more than just the 16 bytes we found. If KVM_S390_CMMA_PEEK is set: the existing storage attributes are read even when not in migration mode, and no other action is performed; the output start_gfn will be equal to the input start_gfn, the output count will be equal to the input count, except if the end of memory has been reached. In both cases: the field "remaining" will indicate the total number of dirty CMMA values still remaining, or 0 if KVM_S390_CMMA_PEEK is set and migration mode is not enabled. mask is unused. values points to the userspace buffer where the result will be stored. This ioctl can fail with -ENOMEM if not enough memory can be allocated to complete the task, with -ENXIO if CMMA is not enabled, with -EINVAL if KVM_S390_CMMA_PEEK is not set but migration mode was not enabled, with -EFAULT if the userspace address is invalid or if no page table is present for the addresses (e.g. when using hugepages). 4.108 KVM_S390_SET_CMMA_BITS Capability: KVM_CAP_S390_CMMA_MIGRATION Architectures: s390 Type: vm ioctl Parameters: struct kvm_s390_cmma_log (in) Returns: 0 on success, a negative value on error This ioctl is used to set the values of the CMMA bits on the s390 architecture. It is meant to be used during live migration to restore the CMMA values, but there are no restrictions on its use. The ioctl takes parameters via the kvm_s390_cmma_values struct. Each CMMA value takes up one byte. struct kvm_s390_cmma_log { __u64 start_gfn; __u32 count; __u32 flags; union { __u64 remaining; __u64 mask; }; __u64 values; }; start_gfn indicates the starting guest frame number, count indicates how many values are to be considered in the buffer, flags is not used and must be 0. mask indicates which PGSTE bits are to be considered. remaining is not used. values points to the buffer in userspace where to store the values. This ioctl can fail with -ENOMEM if not enough memory can be allocated to complete the task, with -ENXIO if CMMA is not enabled, with -EINVAL if the count field is too large (e.g. more than KVM_S390_CMMA_SIZE_MAX) or if the flags field was not 0, with -EFAULT if the userspace address is invalid, if invalid pages are written to (e.g. after the end of memory) or if no page table is present for the addresses (e.g. when using hugepages). 4.109 KVM_PPC_GET_CPU_CHAR Capability: KVM_CAP_PPC_GET_CPU_CHAR Architectures: powerpc Type: vm ioctl Parameters: struct kvm_ppc_cpu_char (out) Returns: 0 on successful completion -EFAULT if struct kvm_ppc_cpu_char cannot be written This ioctl gives userspace information about certain characteristics of the CPU relating to speculative execution of instructions and possible information leakage resulting from speculative execution (see CVE-2017-5715, CVE-2017-5753 and CVE-2017-5754). The information is returned in struct kvm_ppc_cpu_char, which looks like this: struct kvm_ppc_cpu_char { __u64 character; /* characteristics of the CPU */ __u64 behaviour; /* recommended software behaviour */ __u64 character_mask; /* valid bits in character */ __u64 behaviour_mask; /* valid bits in behaviour */ }; For extensibility, the character_mask and behaviour_mask fields indicate which bits of character and behaviour have been filled in by the kernel. If the set of defined bits is extended in future then userspace will be able to tell whether it is running on a kernel that knows about the new bits. The character field describes attributes of the CPU which can help with preventing inadvertent information disclosure - specifically, whether there is an instruction to flash-invalidate the L1 data cache (ori 30,30,0 or mtspr SPRN_TRIG2,rN), whether the L1 data cache is set to a mode where entries can only be used by the thread that created them, whether the bcctr[l] instruction prevents speculation, and whether a speculation barrier instruction (ori 31,31,0) is provided. The behaviour field describes actions that software should take to prevent inadvertent information disclosure, and thus describes which vulnerabilities the hardware is subject to; specifically whether the L1 data cache should be flushed when returning to user mode from the kernel, and whether a speculation barrier should be placed between an array bounds check and the array access. These fields use the same bit definitions as the new H_GET_CPU_CHARACTERISTICS hypercall. 4.110 KVM_MEMORY_ENCRYPT_OP Capability: basic Architectures: x86 Type: system Parameters: an opaque platform specific structure (in/out) Returns: 0 on success; -1 on error If the platform supports creating encrypted VMs then this ioctl can be used for issuing platform-specific memory encryption commands to manage those encrypted VMs. Currently, this ioctl is used for issuing Secure Encrypted Virtualization (SEV) commands on AMD Processors. The SEV commands are defined in Documentation/virtual/kvm/amd-memory-encryption.txt. 4.111 KVM_MEMORY_ENCRYPT_REG_REGION Capability: basic Architectures: x86 Type: system Parameters: struct kvm_enc_region (in) Returns: 0 on success; -1 on error This ioctl can be used to register a guest memory region which may contain encrypted data (e.g. guest RAM, SMRAM etc). It is used in the SEV-enabled guest. When encryption is enabled, a guest memory region may contain encrypted data. The SEV memory encryption engine uses a tweak such that two identical plaintext pages, each at different locations will have differing ciphertexts. So swapping or moving ciphertext of those pages will not result in plaintext being swapped. So relocating (or migrating) physical backing pages for the SEV guest will require some additional steps. Note: The current SEV key management spec does not provide commands to swap or migrate (move) ciphertext pages. Hence, for now we pin the guest memory region registered with the ioctl. 4.112 KVM_MEMORY_ENCRYPT_UNREG_REGION Capability: basic Architectures: x86 Type: system Parameters: struct kvm_enc_region (in) Returns: 0 on success; -1 on error This ioctl can be used to unregister the guest memory region registered with KVM_MEMORY_ENCRYPT_REG_REGION ioctl above. 5. The kvm_run structure ------------------------ Application code obtains a pointer to the kvm_run structure by mmap()ing a vcpu fd. From that point, application code can control execution by changing fields in kvm_run prior to calling the KVM_RUN ioctl, and obtain information about the reason KVM_RUN returned by looking up structure members. struct kvm_run { /* in */ __u8 request_interrupt_window; Request that KVM_RUN return when it becomes possible to inject external interrupts into the guest. Useful in conjunction with KVM_INTERRUPT. __u8 immediate_exit; This field is polled once when KVM_RUN starts; if non-zero, KVM_RUN exits immediately, returning -EINTR. In the common scenario where a signal is used to "kick" a VCPU out of KVM_RUN, this field can be used to avoid usage of KVM_SET_SIGNAL_MASK, which has worse scalability. Rather than blocking the signal outside KVM_RUN, userspace can set up a signal handler that sets run->immediate_exit to a non-zero value. This field is ignored if KVM_CAP_IMMEDIATE_EXIT is not available. __u8 padding1[6]; /* out */ __u32 exit_reason; When KVM_RUN has returned successfully (return value 0), this informs application code why KVM_RUN has returned. Allowable values for this field are detailed below. __u8 ready_for_interrupt_injection; If request_interrupt_window has been specified, this field indicates an interrupt can be injected now with KVM_INTERRUPT. __u8 if_flag; The value of the current interrupt flag. Only valid if in-kernel local APIC is not used. __u16 flags; More architecture-specific flags detailing state of the VCPU that may affect the device's behavior. The only currently defined flag is KVM_RUN_X86_SMM, which is valid on x86 machines and is set if the VCPU is in system management mode. /* in (pre_kvm_run), out (post_kvm_run) */ __u64 cr8; The value of the cr8 register. Only valid if in-kernel local APIC is not used. Both input and output. __u64 apic_base; The value of the APIC BASE msr. Only valid if in-kernel local APIC is not used. Both input and output. union { /* KVM_EXIT_UNKNOWN */ struct { __u64 hardware_exit_reason; } hw; If exit_reason is KVM_EXIT_UNKNOWN, the vcpu has exited due to unknown reasons. Further architecture-specific information is available in hardware_exit_reason. /* KVM_EXIT_FAIL_ENTRY */ struct { __u64 hardware_entry_failure_reason; } fail_entry; If exit_reason is KVM_EXIT_FAIL_ENTRY, the vcpu could not be run due to unknown reasons. Further architecture-specific information is available in hardware_entry_failure_reason. /* KVM_EXIT_EXCEPTION */ struct { __u32 exception; __u32 error_code; } ex; Unused. /* KVM_EXIT_IO */ struct { #define KVM_EXIT_IO_IN 0 #define KVM_EXIT_IO_OUT 1 __u8 direction; __u8 size; /* bytes */ __u16 port; __u32 count; __u64 data_offset; /* relative to kvm_run start */ } io; If exit_reason is KVM_EXIT_IO, then the vcpu has executed a port I/O instruction which could not be satisfied by kvm. data_offset describes where the data is located (KVM_EXIT_IO_OUT) or where kvm expects application code to place the data for the next KVM_RUN invocation (KVM_EXIT_IO_IN). Data format is a packed array. /* KVM_EXIT_DEBUG */ struct { struct kvm_debug_exit_arch arch; } debug; If the exit_reason is KVM_EXIT_DEBUG, then a vcpu is processing a debug event for which architecture specific information is returned. /* KVM_EXIT_MMIO */ struct { __u64 phys_addr; __u8 data[8]; __u32 len; __u8 is_write; } mmio; If exit_reason is KVM_EXIT_MMIO, then the vcpu has executed a memory-mapped I/O instruction which could not be satisfied by kvm. The 'data' member contains the written data if 'is_write' is true, and should be filled by application code otherwise. The 'data' member contains, in its first 'len' bytes, the value as it would appear if the VCPU performed a load or store of the appropriate width directly to the byte array. NOTE: For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR and KVM_EXIT_EPR the corresponding operations are complete (and guest state is consistent) only after userspace has re-entered the kernel with KVM_RUN. The kernel side will first finish incomplete operations and then check for pending signals. Userspace can re-enter the guest with an unmasked signal pending to complete pending operations. /* KVM_EXIT_HYPERCALL */ struct { __u64 nr; __u64 args[6]; __u64 ret; __u32 longmode; __u32 pad; } hypercall; Unused. This was once used for 'hypercall to userspace'. To implement such functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390). Note KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO. /* KVM_EXIT_TPR_ACCESS */ struct { __u64 rip; __u32 is_write; __u32 pad; } tpr_access; To be documented (KVM_TPR_ACCESS_REPORTING). /* KVM_EXIT_S390_SIEIC */ struct { __u8 icptcode; __u64 mask; /* psw upper half */ __u64 addr; /* psw lower half */ __u16 ipa; __u32 ipb; } s390_sieic; s390 specific. /* KVM_EXIT_S390_RESET */ #define KVM_S390_RESET_POR 1 #define KVM_S390_RESET_CLEAR 2 #define KVM_S390_RESET_SUBSYSTEM 4 #define KVM_S390_RESET_CPU_INIT 8 #define KVM_S390_RESET_IPL 16 __u64 s390_reset_flags; s390 specific. /* KVM_EXIT_S390_UCONTROL */ struct { __u64 trans_exc_code; __u32 pgm_code; } s390_ucontrol; s390 specific. A page fault has occurred for a user controlled virtual machine (KVM_VM_S390_UNCONTROL) on it's host page table that cannot be resolved by the kernel. The program code and the translation exception code that were placed in the cpu's lowcore are presented here as defined by the z Architecture Principles of Operation Book in the Chapter for Dynamic Address Translation (DAT) /* KVM_EXIT_DCR */ struct { __u32 dcrn; __u32 data; __u8 is_write; } dcr; Deprecated - was used for 440 KVM. /* KVM_EXIT_OSI */ struct { __u64 gprs[32]; } osi; MOL uses a special hypercall interface it calls 'OSI'. To enable it, we catch hypercalls and exit with this exit struct that contains all the guest gprs. If exit_reason is KVM_EXIT_OSI, then the vcpu has triggered such a hypercall. Userspace can now handle the hypercall and when it's done modify the gprs as necessary. Upon guest entry all guest GPRs will then be replaced by the values in this struct. /* KVM_EXIT_PAPR_HCALL */ struct { __u64 nr; __u64 ret; __u64 args[9]; } papr_hcall; This is used on 64-bit PowerPC when emulating a pSeries partition, e.g. with the 'pseries' machine type in qemu. It occurs when the guest does a hypercall using the 'sc 1' instruction. The 'nr' field contains the hypercall number (from the guest R3), and 'args' contains the arguments (from the guest R4 - R12). Userspace should put the return code in 'ret' and any extra returned values in args[]. The possible hypercalls are defined in the Power Architecture Platform Requirements (PAPR) document available from www.power.org (free developer registration required to access it). /* KVM_EXIT_S390_TSCH */ struct { __u16 subchannel_id; __u16 subchannel_nr; __u32 io_int_parm; __u32 io_int_word; __u32 ipb; __u8 dequeued; } s390_tsch; s390 specific. This exit occurs when KVM_CAP_S390_CSS_SUPPORT has been enabled and TEST SUBCHANNEL was intercepted. If dequeued is set, a pending I/O interrupt for the target subchannel has been dequeued and subchannel_id, subchannel_nr, io_int_parm and io_int_word contain the parameters for that interrupt. ipb is needed for instruction parameter decoding. /* KVM_EXIT_EPR */ struct { __u32 epr; } epr; On FSL BookE PowerPC chips, the interrupt controller has a fast patch interrupt acknowledge path to the core. When the core successfully delivers an interrupt, it automatically populates the EPR register with the interrupt vector number and acknowledges the interrupt inside the interrupt controller. In case the interrupt controller lives in user space, we need to do the interrupt acknowledge cycle through it to fetch the next to be delivered interrupt vector using this exit. It gets triggered whenever both KVM_CAP_PPC_EPR are enabled and an external interrupt has just been delivered into the guest. User space should put the acknowledged interrupt vector into the 'epr' field. /* KVM_EXIT_SYSTEM_EVENT */ struct { #define KVM_SYSTEM_EVENT_SHUTDOWN 1 #define KVM_SYSTEM_EVENT_RESET 2 #define KVM_SYSTEM_EVENT_CRASH 3 __u32 type; __u64 flags; } system_event; If exit_reason is KVM_EXIT_SYSTEM_EVENT then the vcpu has triggered a system-level event using some architecture specific mechanism (hypercall or some special instruction). In case of ARM/ARM64, this is triggered using HVC instruction based PSCI call from the vcpu. The 'type' field describes the system-level event type. The 'flags' field describes architecture specific flags for the system-level event. Valid values for 'type' are: KVM_SYSTEM_EVENT_SHUTDOWN -- the guest has requested a shutdown of the VM. Userspace is not obliged to honour this, and if it does honour this does not need to destroy the VM synchronously (ie it may call KVM_RUN again before shutdown finally occurs). KVM_SYSTEM_EVENT_RESET -- the guest has requested a reset of the VM. As with SHUTDOWN, userspace can choose to ignore the request, or to schedule the reset to occur in the future and may call KVM_RUN again. KVM_SYSTEM_EVENT_CRASH -- the guest crash occurred and the guest has requested a crash condition maintenance. Userspace can choose to ignore the request, or to gather VM memory core dump and/or reset/shutdown of the VM. /* KVM_EXIT_IOAPIC_EOI */ struct { __u8 vector; } eoi; Indicates that the VCPU's in-kernel local APIC received an EOI for a level-triggered IOAPIC interrupt. This exit only triggers when the IOAPIC is implemented in userspace (i.e. KVM_CAP_SPLIT_IRQCHIP is enabled); the userspace IOAPIC should process the EOI and retrigger the interrupt if it is still asserted. Vector is the LAPIC interrupt vector for which the EOI was received. struct kvm_hyperv_exit { #define KVM_EXIT_HYPERV_SYNIC 1 #define KVM_EXIT_HYPERV_HCALL 2 __u32 type; union { struct { __u32 msr; __u64 control; __u64 evt_page; __u64 msg_page; } synic; struct { __u64 input; __u64 result; __u64 params[2]; } hcall; } u; }; /* KVM_EXIT_HYPERV */ struct kvm_hyperv_exit hyperv; Indicates that the VCPU exits into userspace to process some tasks related to Hyper-V emulation. Valid values for 'type' are: KVM_EXIT_HYPERV_SYNIC -- synchronously notify user-space about Hyper-V SynIC state change. Notification is used to remap SynIC event/message pages and to enable/disable SynIC messages/events processing in userspace. /* Fix the size of the union. */ char padding[256]; }; /* * shared registers between kvm and userspace. * kvm_valid_regs specifies the register classes set by the host * kvm_dirty_regs specified the register classes dirtied by userspace * struct kvm_sync_regs is architecture specific, as well as the * bits for kvm_valid_regs and kvm_dirty_regs */ __u64 kvm_valid_regs; __u64 kvm_dirty_regs; union { struct kvm_sync_regs regs; char padding[1024]; } s; If KVM_CAP_SYNC_REGS is defined, these fields allow userspace to access certain guest registers without having to call SET/GET_*REGS. Thus we can avoid some system call overhead if userspace has to handle the exit. Userspace can query the validity of the structure by checking kvm_valid_regs for specific bits. These bits are architecture specific and usually define the validity of a groups of registers. (e.g. one bit for general purpose registers) Please note that the kernel is allowed to use the kvm_run structure as the primary storage for certain register types. Therefore, the kernel may use the values in kvm_run even if the corresponding bit in kvm_dirty_regs is not set. }; 6. Capabilities that can be enabled on vCPUs -------------------------------------------- There are certain capabilities that change the behavior of the virtual CPU or the virtual machine when enabled. To enable them, please see section 4.37. Below you can find a list of capabilities and what their effect on the vCPU or the virtual machine is when enabling them. The following information is provided along with the description: Architectures: which instruction set architectures provide this ioctl. x86 includes both i386 and x86_64. Target: whether this is a per-vcpu or per-vm capability. Parameters: what parameters are accepted by the capability. Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL) are not detailed, but errors with specific meanings are. 6.1 KVM_CAP_PPC_OSI Architectures: ppc Target: vcpu Parameters: none Returns: 0 on success; -1 on error This capability enables interception of OSI hypercalls that otherwise would be treated as normal system calls to be injected into the guest. OSI hypercalls were invented by Mac-on-Linux to have a standardized communication mechanism between the guest and the host. When this capability is enabled, KVM_EXIT_OSI can occur. 6.2 KVM_CAP_PPC_PAPR Architectures: ppc Target: vcpu Parameters: none Returns: 0 on success; -1 on error This capability enables interception of PAPR hypercalls. PAPR hypercalls are done using the hypercall instruction "sc 1". It also sets the guest privilege level to "supervisor" mode. Usually the guest runs in "hypervisor" privilege mode with a few missing features. In addition to the above, it changes the semantics of SDR1. In this mode, the HTAB address part of SDR1 contains an HVA instead of a GPA, as PAPR keeps the HTAB invisible to the guest. When this capability is enabled, KVM_EXIT_PAPR_HCALL can occur. 6.3 KVM_CAP_SW_TLB Architectures: ppc Target: vcpu Parameters: args[0] is the address of a struct kvm_config_tlb Returns: 0 on success; -1 on error struct kvm_config_tlb { __u64 params; __u64 array; __u32 mmu_type; __u32 array_len; }; Configures the virtual CPU's TLB array, establishing a shared memory area between userspace and KVM. The "params" and "array" fields are userspace addresses of mmu-type-specific data structures. The "array_len" field is an safety mechanism, and should be set to the size in bytes of the memory that userspace has reserved for the array. It must be at least the size dictated by "mmu_type" and "params". While KVM_RUN is active, the shared region is under control of KVM. Its contents are undefined, and any modification by userspace results in boundedly undefined behavior. On return from KVM_RUN, the shared region will reflect the current state of the guest's TLB. If userspace makes any changes, it must call KVM_DIRTY_TLB to tell KVM which entries have been changed, prior to calling KVM_RUN again on this vcpu. For mmu types KVM_MMU_FSL_BOOKE_NOHV and KVM_MMU_FSL_BOOKE_HV: - The "params" field is of type "struct kvm_book3e_206_tlb_params". - The "array" field points to an array of type "struct kvm_book3e_206_tlb_entry". - The array consists of all entries in the first TLB, followed by all entries in the second TLB. - Within a TLB, entries are ordered first by increasing set number. Within a set, entries are ordered by way (increasing ESEL). - The hash for determining set number in TLB0 is: (MAS2 >> 12) & (num_sets - 1) where "num_sets" is the tlb_sizes[] value divided by the tlb_ways[] value. - The tsize field of mas1 shall be set to 4K on TLB0, even though the hardware ignores this value for TLB0. 6.4 KVM_CAP_S390_CSS_SUPPORT Architectures: s390 Target: vcpu Parameters: none Returns: 0 on success; -1 on error This capability enables support for handling of channel I/O instructions. TEST PENDING INTERRUPTION and the interrupt portion of TEST SUBCHANNEL are handled in-kernel, while the other I/O instructions are passed to userspace. When this capability is enabled, KVM_EXIT_S390_TSCH will occur on TEST SUBCHANNEL intercepts. Note that even though this capability is enabled per-vcpu, the complete virtual machine is affected. 6.5 KVM_CAP_PPC_EPR Architectures: ppc Target: vcpu Parameters: args[0] defines whether the proxy facility is active Returns: 0 on success; -1 on error This capability enables or disables the delivery of interrupts through the external proxy facility. When enabled (args[0] != 0), every time the guest gets an external interrupt delivered, it automatically exits into user space with a KVM_EXIT_EPR exit to receive the topmost interrupt vector. When disabled (args[0] == 0), behavior is as if this facility is unsupported. When this capability is enabled, KVM_EXIT_EPR can occur. 6.6 KVM_CAP_IRQ_MPIC Architectures: ppc Parameters: args[0] is the MPIC device fd args[1] is the MPIC CPU number for this vcpu This capability connects the vcpu to an in-kernel MPIC device. 6.7 KVM_CAP_IRQ_XICS Architectures: ppc Target: vcpu Parameters: args[0] is the XICS device fd args[1] is the XICS CPU number (server ID) for this vcpu This capability connects the vcpu to an in-kernel XICS device. 6.8 KVM_CAP_S390_IRQCHIP Architectures: s390 Target: vm Parameters: none This capability enables the in-kernel irqchip for s390. Please refer to "4.24 KVM_CREATE_IRQCHIP" for details. 6.9 KVM_CAP_MIPS_FPU Architectures: mips Target: vcpu Parameters: args[0] is reserved for future use (should be 0). This capability allows the use of the host Floating Point Unit by the guest. It allows the Config1.FP bit to be set to enable the FPU in the guest. Once this is done the KVM_REG_MIPS_FPR_* and KVM_REG_MIPS_FCR_* registers can be accessed (depending on the current guest FPU register mode), and the Status.FR, Config5.FRE bits are accessible via the KVM API and also from the guest, depending on them being supported by the FPU. 6.10 KVM_CAP_MIPS_MSA Architectures: mips Target: vcpu Parameters: args[0] is reserved for future use (should be 0). This capability allows the use of the MIPS SIMD Architecture (MSA) by the guest. It allows the Config3.MSAP bit to be set to enable the use of MSA by the guest. Once this is done the KVM_REG_MIPS_VEC_* and KVM_REG_MIPS_MSA_* registers can be accessed, and the Config5.MSAEn bit is accessible via the KVM API and also from the guest. 7. Capabilities that can be enabled on VMs ------------------------------------------ There are certain capabilities that change the behavior of the virtual machine when enabled. To enable them, please see section 4.37. Below you can find a list of capabilities and what their effect on the VM is when enabling them. The following information is provided along with the description: Architectures: which instruction set architectures provide this ioctl. x86 includes both i386 and x86_64. Parameters: what parameters are accepted by the capability. Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL) are not detailed, but errors with specific meanings are. 7.1 KVM_CAP_PPC_ENABLE_HCALL Architectures: ppc Parameters: args[0] is the sPAPR hcall number args[1] is 0 to disable, 1 to enable in-kernel handling This capability controls whether individual sPAPR hypercalls (hcalls) get handled by the kernel or not. Enabling or disabling in-kernel handling of an hcall is effective across the VM. On creation, an initial set of hcalls are enabled for in-kernel handling, which consists of those hcalls for which in-kernel handlers were implemented before this capability was implemented. If disabled, the kernel will not to attempt to handle the hcall, but will always exit to userspace to handle it. Note that it may not make sense to enable some and disable others of a group of related hcalls, but KVM does not prevent userspace from doing that. If the hcall number specified is not one that has an in-kernel implementation, the KVM_ENABLE_CAP ioctl will fail with an EINVAL error. 7.2 KVM_CAP_S390_USER_SIGP Architectures: s390 Parameters: none This capability controls which SIGP orders will be handled completely in user space. With this capability enabled, all fast orders will be handled completely in the kernel: - SENSE - SENSE RUNNING - EXTERNAL CALL - EMERGENCY SIGNAL - CONDITIONAL EMERGENCY SIGNAL All other orders will be handled completely in user space. Only privileged operation exceptions will be checked for in the kernel (or even in the hardware prior to interception). If this capability is not enabled, the old way of handling SIGP orders is used (partially in kernel and user space). 7.3 KVM_CAP_S390_VECTOR_REGISTERS Architectures: s390 Parameters: none Returns: 0 on success, negative value on error Allows use of the vector registers introduced with z13 processor, and provides for the synchronization between host and user space. Will return -EINVAL if the machine does not support vectors. 7.4 KVM_CAP_S390_USER_STSI Architectures: s390 Parameters: none This capability allows post-handlers for the STSI instruction. After initial handling in the kernel, KVM exits to user space with KVM_EXIT_S390_STSI to allow user space to insert further data. Before exiting to userspace, kvm handlers should fill in s390_stsi field of vcpu->run: struct { __u64 addr; __u8 ar; __u8 reserved; __u8 fc; __u8 sel1; __u16 sel2; } s390_stsi; @addr - guest address of STSI SYSIB @fc - function code @sel1 - selector 1 @sel2 - selector 2 @ar - access register number KVM handlers should exit to userspace with rc = -EREMOTE. 7.5 KVM_CAP_SPLIT_IRQCHIP Architectures: x86 Parameters: args[0] - number of routes reserved for userspace IOAPICs Returns: 0 on success, -1 on error Create a local apic for each processor in the kernel. This can be used instead of KVM_CREATE_IRQCHIP if the userspace VMM wishes to emulate the IOAPIC and PIC (and also the PIT, even though this has to be enabled separately). This capability also enables in kernel routing of interrupt requests; when KVM_CAP_SPLIT_IRQCHIP only routes of KVM_IRQ_ROUTING_MSI type are used in the IRQ routing table. The first args[0] MSI routes are reserved for the IOAPIC pins. Whenever the LAPIC receives an EOI for these routes, a KVM_EXIT_IOAPIC_EOI vmexit will be reported to userspace. Fails if VCPU has already been created, or if the irqchip is already in the kernel (i.e. KVM_CREATE_IRQCHIP has already been called). 7.6 KVM_CAP_S390_RI Architectures: s390 Parameters: none Allows use of runtime-instrumentation introduced with zEC12 processor. Will return -EINVAL if the machine does not support runtime-instrumentation. Will return -EBUSY if a VCPU has already been created. 7.7 KVM_CAP_X2APIC_API Architectures: x86 Parameters: args[0] - features that should be enabled Returns: 0 on success, -EINVAL when args[0] contains invalid features Valid feature flags in args[0] are #define KVM_X2APIC_API_USE_32BIT_IDS (1ULL << 0) #define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1) Enabling KVM_X2APIC_API_USE_32BIT_IDS changes the behavior of KVM_SET_GSI_ROUTING, KVM_SIGNAL_MSI, KVM_SET_LAPIC, and KVM_GET_LAPIC, allowing the use of 32-bit APIC IDs. See KVM_CAP_X2APIC_API in their respective sections. KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK must be enabled for x2APIC to work in logical mode or with more than 255 VCPUs. Otherwise, KVM treats 0xff as a broadcast even in x2APIC mode in order to support physical x2APIC without interrupt remapping. This is undesirable in logical mode, where 0xff represents CPUs 0-7 in cluster 0. 7.8 KVM_CAP_S390_USER_INSTR0 Architectures: s390 Parameters: none With this capability enabled, all illegal instructions 0x0000 (2 bytes) will be intercepted and forwarded to user space. User space can use this mechanism e.g. to realize 2-byte software breakpoints. The kernel will not inject an operating exception for these instructions, user space has to take care of that. This capability can be enabled dynamically even if VCPUs were already created and are running. 7.9 KVM_CAP_S390_GS Architectures: s390 Parameters: none Returns: 0 on success; -EINVAL if the machine does not support guarded storage; -EBUSY if a VCPU has already been created. Allows use of guarded storage for the KVM guest. 7.10 KVM_CAP_S390_AIS Architectures: s390 Parameters: none Allow use of adapter-interruption suppression. Returns: 0 on success; -EBUSY if a VCPU has already been created. 7.11 KVM_CAP_PPC_SMT Architectures: ppc Parameters: vsmt_mode, flags Enabling this capability on a VM provides userspace with a way to set the desired virtual SMT mode (i.e. the number of virtual CPUs per virtual core). The virtual SMT mode, vsmt_mode, must be a power of 2 between 1 and 8. On POWER8, vsmt_mode must also be no greater than the number of threads per subcore for the host. Currently flags must be 0. A successful call to enable this capability will result in vsmt_mode being returned when the KVM_CAP_PPC_SMT capability is subsequently queried for the VM. This capability is only supported by HV KVM, and can only be set before any VCPUs have been created. The KVM_CAP_PPC_SMT_POSSIBLE capability indicates which virtual SMT modes are available. 7.12 KVM_CAP_PPC_FWNMI Architectures: ppc Parameters: none With this capability a machine check exception in the guest address space will cause KVM to exit the guest with NMI exit reason. This enables QEMU to build error log and branch to guest kernel registered machine check handling routine. Without this capability KVM will branch to guests' 0x200 interrupt vector. 8. Other capabilities. ---------------------- This section lists capabilities that give information about other features of the KVM implementation. 8.1 KVM_CAP_PPC_HWRNG Architectures: ppc This capability, if KVM_CHECK_EXTENSION indicates that it is available, means that that the kernel has an implementation of the H_RANDOM hypercall backed by a hardware random-number generator. If present, the kernel H_RANDOM handler can be enabled for guest use with the KVM_CAP_PPC_ENABLE_HCALL capability. 8.2 KVM_CAP_HYPERV_SYNIC Architectures: x86 This capability, if KVM_CHECK_EXTENSION indicates that it is available, means that that the kernel has an implementation of the Hyper-V Synthetic interrupt controller(SynIC). Hyper-V SynIC is used to support Windows Hyper-V based guest paravirt drivers(VMBus). In order to use SynIC, it has to be activated by setting this capability via KVM_ENABLE_CAP ioctl on the vcpu fd. Note that this will disable the use of APIC hardware virtualization even if supported by the CPU, as it's incompatible with SynIC auto-EOI behavior. 8.3 KVM_CAP_PPC_RADIX_MMU Architectures: ppc This capability, if KVM_CHECK_EXTENSION indicates that it is available, means that that the kernel can support guests using the radix MMU defined in Power ISA V3.00 (as implemented in the POWER9 processor). 8.4 KVM_CAP_PPC_HASH_MMU_V3 Architectures: ppc This capability, if KVM_CHECK_EXTENSION indicates that it is available, means that that the kernel can support guests using the hashed page table MMU defined in Power ISA V3.00 (as implemented in the POWER9 processor), including in-memory segment tables. 8.5 KVM_CAP_MIPS_VZ Architectures: mips This capability, if KVM_CHECK_EXTENSION on the main kvm handle indicates that it is available, means that full hardware assisted virtualization capabilities of the hardware are available for use through KVM. An appropriate KVM_VM_MIPS_* type must be passed to KVM_CREATE_VM to create a VM which utilises it. If KVM_CHECK_EXTENSION on a kvm VM handle indicates that this capability is available, it means that the VM is using full hardware assisted virtualization capabilities of the hardware. This is useful to check after creating a VM with KVM_VM_MIPS_DEFAULT. The value returned by KVM_CHECK_EXTENSION should be compared against known values (see below). All other values are reserved. This is to allow for the possibility of other hardware assisted virtualization implementations which may be incompatible with the MIPS VZ ASE. 0: The trap & emulate implementation is in use to run guest code in user mode. Guest virtual memory segments are rearranged to fit the guest in the user mode address space. 1: The MIPS VZ ASE is in use, providing full hardware assisted virtualization, including standard guest virtual memory segments. 8.6 KVM_CAP_MIPS_TE Architectures: mips This capability, if KVM_CHECK_EXTENSION on the main kvm handle indicates that it is available, means that the trap & emulate implementation is available to run guest code in user mode, even if KVM_CAP_MIPS_VZ indicates that hardware assisted virtualisation is also available. KVM_VM_MIPS_TE (0) must be passed to KVM_CREATE_VM to create a VM which utilises it. If KVM_CHECK_EXTENSION on a kvm VM handle indicates that this capability is available, it means that the VM is using trap & emulate. 8.7 KVM_CAP_MIPS_64BIT Architectures: mips This capability indicates the supported architecture type of the guest, i.e. the supported register and address width. The values returned when this capability is checked by KVM_CHECK_EXTENSION on a kvm VM handle correspond roughly to the CP0_Config.AT register field, and should be checked specifically against known values (see below). All other values are reserved. 0: MIPS32 or microMIPS32. Both registers and addresses are 32-bits wide. It will only be possible to run 32-bit guest code. 1: MIPS64 or microMIPS64 with access only to 32-bit compatibility segments. Registers are 64-bits wide, but addresses are 32-bits wide. 64-bit guest code may run but cannot access MIPS64 memory segments. It will also be possible to run 32-bit guest code. 2: MIPS64 or microMIPS64 with access to all address segments. Both registers and addresses are 64-bits wide. It will be possible to run 64-bit or 32-bit guest code. 8.8 KVM_CAP_X86_GUEST_MWAIT Architectures: x86 This capability indicates that guest using memory monotoring instructions (MWAIT/MWAITX) to stop the virtual CPU will not cause a VM exit. As such time spent while virtual CPU is halted in this way will then be accounted for as guest running time on the host (as opposed to e.g. HLT). 8.9 KVM_CAP_ARM_USER_IRQ Architectures: arm, arm64 This capability, if KVM_CHECK_EXTENSION indicates that it is available, means that if userspace creates a VM without an in-kernel interrupt controller, it will be notified of changes to the output level of in-kernel emulated devices, which can generate virtual interrupts, presented to the VM. For such VMs, on every return to userspace, the kernel updates the vcpu's run->s.regs.device_irq_level field to represent the actual output level of the device. Whenever kvm detects a change in the device output level, kvm guarantees at least one return to userspace before running the VM. This exit could either be a KVM_EXIT_INTR or any other exit event, like KVM_EXIT_MMIO. This way, userspace can always sample the device output level and re-compute the state of the userspace interrupt controller. Userspace should always check the state of run->s.regs.device_irq_level on every kvm exit. The value in run->s.regs.device_irq_level can represent both level and edge triggered interrupt signals, depending on the device. Edge triggered interrupt signals will exit to userspace with the bit in run->s.regs.device_irq_level set exactly once per edge signal. The field run->s.regs.device_irq_level is available independent of run->kvm_valid_regs or run->kvm_dirty_regs bits. If KVM_CAP_ARM_USER_IRQ is supported, the KVM_CHECK_EXTENSION ioctl returns a number larger than 0 indicating the version of this capability is implemented and thereby which bits in in run->s.regs.device_irq_level can signal values. Currently the following bits are defined for the device_irq_level bitmap: KVM_CAP_ARM_USER_IRQ >= 1: KVM_ARM_DEV_EL1_VTIMER - EL1 virtual timer KVM_ARM_DEV_EL1_PTIMER - EL1 physical timer KVM_ARM_DEV_PMU - ARM PMU overflow interrupt signal Future versions of kvm may implement additional events. These will get indicated by returning a higher number from KVM_CHECK_EXTENSION and will be listed above. 8.10 KVM_CAP_PPC_SMT_POSSIBLE Architectures: ppc Querying this capability returns a bitmap indicating the possible virtual SMT modes that can be set using KVM_CAP_PPC_SMT. If bit N (counting from the right) is set, then a virtual SMT mode of 2^N is available. 8.11 KVM_CAP_HYPERV_SYNIC2 Architectures: x86 This capability enables a newer version of Hyper-V Synthetic interrupt controller (SynIC). The only difference with KVM_CAP_HYPERV_SYNIC is that KVM doesn't clear SynIC message and event flags pages when they are enabled by writing to the respective MSRs. 8.12 KVM_CAP_HYPERV_VP_INDEX Architectures: x86 This capability indicates that userspace can load HV_X64_MSR_VP_INDEX msr. Its value is used to denote the target vcpu for a SynIC interrupt. For compatibilty, KVM initializes this msr to KVM's internal vcpu index. When this capability is absent, userspace can still query this msr's value. 8.13 KVM_CAP_S390_AIS_MIGRATION Architectures: s390 Parameters: none This capability indicates if the flic device will be able to get/set the AIS states for migration via the KVM_DEV_FLIC_AISM_ALL attribute and allows to discover this without having to create a flic device.