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-rw-r--r--Documentation/virt/kvm/api.rst276
1 files changed, 210 insertions, 66 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 9f3172376ec3..07a45474abe9 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -417,7 +417,7 @@ kvm_run' (see below).
-----------------
:Capability: basic
-:Architectures: all except ARM, arm64
+:Architectures: all except arm64
:Type: vcpu ioctl
:Parameters: struct kvm_regs (out)
:Returns: 0 on success, -1 on error
@@ -450,7 +450,7 @@ Reads the general purpose registers from the vcpu.
-----------------
:Capability: basic
-:Architectures: all except ARM, arm64
+:Architectures: all except arm64
:Type: vcpu ioctl
:Parameters: struct kvm_regs (in)
:Returns: 0 on success, -1 on error
@@ -824,7 +824,7 @@ Writes the floating point state to the vcpu.
-----------------------
:Capability: KVM_CAP_IRQCHIP, KVM_CAP_S390_IRQCHIP (s390)
-:Architectures: x86, ARM, arm64, s390
+:Architectures: x86, arm64, s390
:Type: vm ioctl
:Parameters: none
:Returns: 0 on success, -1 on error
@@ -833,7 +833,7 @@ 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
+On 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.
@@ -846,7 +846,7 @@ before KVM_CREATE_IRQCHIP can be used.
-----------------
:Capability: KVM_CAP_IRQCHIP
-:Architectures: x86, arm, arm64
+:Architectures: x86, arm64
:Type: vm ioctl
:Parameters: struct kvm_irq_level
:Returns: 0 on success, -1 on error
@@ -870,7 +870,7 @@ 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
+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::
@@ -896,7 +896,7 @@ When KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 is supported, the target vcpu is
identified as (256 * vcpu2_index + vcpu_index). Otherwise, vcpu2_index
must be zero.
-Note that on arm/arm64, the KVM_CAP_IRQCHIP capability only conditions
+Note that on arm64, the KVM_CAP_IRQCHIP capability only conditions
injection of interrupts for the in-kernel irqchip. KVM_IRQ_LINE can always
be used for a userspace interrupt controller.
@@ -1087,7 +1087,7 @@ Other flags returned by ``KVM_GET_CLOCK`` are accepted but ignored.
:Capability: KVM_CAP_VCPU_EVENTS
:Extended by: KVM_CAP_INTR_SHADOW
-:Architectures: x86, arm, arm64
+:Architectures: x86, arm64
:Type: vcpu ioctl
:Parameters: struct kvm_vcpu_event (out)
:Returns: 0 on success, -1 on error
@@ -1146,8 +1146,8 @@ The following bits are defined in the flags field:
fields contain a valid state. This bit will be set whenever
KVM_CAP_EXCEPTION_PAYLOAD is enabled.
-ARM/ARM64:
-^^^^^^^^^^
+ARM64:
+^^^^^^
If the guest accesses a device that is being emulated by the host kernel in
such a way that a real device would generate a physical SError, KVM may make
@@ -1206,7 +1206,7 @@ directly to the virtual CPU).
:Capability: KVM_CAP_VCPU_EVENTS
:Extended by: KVM_CAP_INTR_SHADOW
-:Architectures: x86, arm, arm64
+:Architectures: x86, arm64
:Type: vcpu ioctl
:Parameters: struct kvm_vcpu_event (in)
:Returns: 0 on success, -1 on error
@@ -1241,8 +1241,8 @@ can be set in the flags field to signal that the
exception_has_payload, exception_payload, and exception.pending fields
contain a valid state and shall be written into the VCPU.
-ARM/ARM64:
-^^^^^^^^^^
+ARM64:
+^^^^^^
User space may need to inject several types of events to the guest.
@@ -1449,7 +1449,7 @@ for vm-wide capabilities.
---------------------
:Capability: KVM_CAP_MP_STATE
-:Architectures: x86, s390, arm, arm64, riscv
+:Architectures: x86, s390, arm64, riscv
:Type: vcpu ioctl
:Parameters: struct kvm_mp_state (out)
:Returns: 0 on success; -1 on error
@@ -1467,7 +1467,7 @@ Possible values are:
========================== ===============================================
KVM_MP_STATE_RUNNABLE the vcpu is currently running
- [x86,arm/arm64,riscv]
+ [x86,arm64,riscv]
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
@@ -1476,7 +1476,7 @@ Possible values are:
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,riscv]
+ KVM_MP_STATE_STOPPED the vcpu is stopped [s390,arm64,riscv]
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]
@@ -1488,8 +1488,8 @@ 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/riscv:
-^^^^^^^^^^^^^^^^^^^^
+For arm64/riscv:
+^^^^^^^^^^^^^^^^
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.
@@ -1498,7 +1498,7 @@ KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not.
---------------------
:Capability: KVM_CAP_MP_STATE
-:Architectures: x86, s390, arm, arm64, riscv
+:Architectures: x86, s390, arm64, riscv
:Type: vcpu ioctl
:Parameters: struct kvm_mp_state (in)
:Returns: 0 on success; -1 on error
@@ -1510,8 +1510,8 @@ 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/riscv:
-^^^^^^^^^^^^^^^^^^^^
+For arm64/riscv:
+^^^^^^^^^^^^^^^^
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.
@@ -1780,14 +1780,14 @@ The flags bitmap is defined as::
------------------------
:Capability: KVM_CAP_IRQ_ROUTING
-:Architectures: x86 s390 arm arm64
+:Architectures: x86 s390 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:
+On arm64, GSI routing has the following limitation:
- GSI routing does not apply to KVM_IRQ_LINE but only to KVM_IRQFD.
@@ -2855,7 +2855,7 @@ after pausing the vcpu, but before it is resumed.
-------------------
:Capability: KVM_CAP_SIGNAL_MSI
-:Architectures: x86 arm arm64
+:Architectures: x86 arm64
:Type: vm ioctl
:Parameters: struct kvm_msi (in)
:Returns: >0 on delivery, 0 if guest blocked the MSI, and -1 on error
@@ -3043,7 +3043,7 @@ into the hash PTE second double word).
--------------
:Capability: KVM_CAP_IRQFD
-:Architectures: x86 s390 arm arm64
+:Architectures: x86 s390 arm64
:Type: vm ioctl
:Parameters: struct kvm_irqfd (in)
:Returns: 0 on success, -1 on error
@@ -3069,7 +3069,7 @@ 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:
+On 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,
@@ -3325,7 +3325,7 @@ current state. "addr" is ignored.
----------------------
:Capability: basic
-:Architectures: arm, arm64
+:Architectures: arm64
:Type: vcpu ioctl
:Parameters: struct kvm_vcpu_init (in)
:Returns: 0 on success; -1 on error
@@ -3423,7 +3423,7 @@ Possible features:
-----------------------------
:Capability: basic
-:Architectures: arm, arm64
+:Architectures: arm64
:Type: vm ioctl
:Parameters: struct kvm_vcpu_init (out)
:Returns: 0 on success; -1 on error
@@ -3452,7 +3452,7 @@ VCPU matching underlying host.
---------------------
:Capability: basic
-:Architectures: arm, arm64, mips
+:Architectures: arm64, mips
:Type: vcpu ioctl
:Parameters: struct kvm_reg_list (in/out)
:Returns: 0 on success; -1 on error
@@ -3479,7 +3479,7 @@ KVM_GET_ONE_REG/KVM_SET_ONE_REG calls.
-----------------------------------------
:Capability: KVM_CAP_ARM_SET_DEVICE_ADDR
-:Architectures: arm, arm64
+:Architectures: arm64
:Type: vm ioctl
:Parameters: struct kvm_arm_device_address (in)
:Returns: 0 on success, -1 on error
@@ -3506,13 +3506,13 @@ 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
+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
+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
@@ -3683,15 +3683,17 @@ The fields in each entry are defined as follows:
4.89 KVM_S390_MEM_OP
--------------------
-:Capability: KVM_CAP_S390_MEM_OP
+:Capability: KVM_CAP_S390_MEM_OP, KVM_CAP_S390_PROTECTED, KVM_CAP_S390_MEM_OP_EXTENSION
:Architectures: s390
-:Type: vcpu ioctl
+:Type: vm ioctl, 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.
+Read or write data from/to the VM's memory.
+The KVM_CAP_S390_MEM_OP_EXTENSION capability specifies what functionality is
+supported.
Parameters are specified via the following structure::
@@ -3701,33 +3703,99 @@ Parameters are specified via the following structure::
__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 */
+ union {
+ struct {
+ __u8 ar; /* the access register number */
+ __u8 key; /* access key, ignored if flag unset */
+ };
+ __u32 sida_offset; /* offset into the sida */
+ __u8 reserved[32]; /* ignored */
+ };
};
-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 (which must not
be 0). The maximum value for "size" can be obtained by checking the
KVM_CAP_S390_MEM_OP capability. "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. When KVM_S390_MEMOP_F_CHECK_ONLY
-is specified, "buf" is unused and can be NULL. "ar" designates the access
-register number to be used; the valid range is 0..15.
+a read access, or where the data that should be written is stored for
+a write access. The "reserved" field is meant for future extensions.
+Reserved and unused values are ignored. Future extension that add members must
+introduce new flags.
+
+The type of operation is specified in the "op" field. Flags modifying
+their behavior can be set in the "flags" field. Undefined flag bits must
+be set to 0.
+
+Possible operations are:
+ * ``KVM_S390_MEMOP_LOGICAL_READ``
+ * ``KVM_S390_MEMOP_LOGICAL_WRITE``
+ * ``KVM_S390_MEMOP_ABSOLUTE_READ``
+ * ``KVM_S390_MEMOP_ABSOLUTE_WRITE``
+ * ``KVM_S390_MEMOP_SIDA_READ``
+ * ``KVM_S390_MEMOP_SIDA_WRITE``
+
+Logical read/write:
+^^^^^^^^^^^^^^^^^^^
+
+Access logical memory, i.e. translate the given guest address to an absolute
+address given the state of the VCPU and use the absolute address as target of
+the access. "ar" designates the access register number to be used; the valid
+range is 0..15.
+Logical accesses are permitted for the VCPU ioctl only.
+Logical accesses are permitted for non-protected guests only.
+
+Supported flags:
+ * ``KVM_S390_MEMOP_F_CHECK_ONLY``
+ * ``KVM_S390_MEMOP_F_INJECT_EXCEPTION``
+ * ``KVM_S390_MEMOP_F_SKEY_PROTECTION``
+
+The KVM_S390_MEMOP_F_CHECK_ONLY flag can be set to check whether the
+corresponding memory access would cause an access exception; however,
+no actual access to the data in memory at the destination is performed.
+In this case, "buf" is unused and can be NULL.
+
+In case an access exception occurred during the access (or would occur
+in case of KVM_S390_MEMOP_F_CHECK_ONLY), the ioctl returns a positive
+error number indicating 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.
+
+If the KVM_S390_MEMOP_F_SKEY_PROTECTION flag is set, storage key
+protection is also in effect and may cause exceptions if accesses are
+prohibited given the access key designated by "key"; the valid range is 0..15.
+KVM_S390_MEMOP_F_SKEY_PROTECTION is available if KVM_CAP_S390_MEM_OP_EXTENSION
+is > 0.
+
+Absolute read/write:
+^^^^^^^^^^^^^^^^^^^^
+
+Access absolute memory. This operation is intended to be used with the
+KVM_S390_MEMOP_F_SKEY_PROTECTION flag, to allow accessing memory and performing
+the checks required for storage key protection as one operation (as opposed to
+user space getting the storage keys, performing the checks, and accessing
+memory thereafter, which could lead to a delay between check and access).
+Absolute accesses are permitted for the VM ioctl if KVM_CAP_S390_MEM_OP_EXTENSION
+is > 0.
+Currently absolute accesses are not permitted for VCPU ioctls.
+Absolute accesses are permitted for non-protected guests only.
+
+Supported flags:
+ * ``KVM_S390_MEMOP_F_CHECK_ONLY``
+ * ``KVM_S390_MEMOP_F_SKEY_PROTECTION``
+
+The semantics of the flags are as for logical accesses.
+
+SIDA read/write:
+^^^^^^^^^^^^^^^^
+
+Access the secure instruction data area which contains memory operands necessary
+for instruction emulation for protected guests.
+SIDA accesses are available if the KVM_CAP_S390_PROTECTED capability is available.
+SIDA accesses are permitted for the VCPU ioctl only.
+SIDA accesses are permitted for protected guests only.
-The "reserved" field is meant for future extensions. It is not used by
-KVM with the currently defined set of flags.
+No flags are supported.
4.90 KVM_S390_GET_SKEYS
-----------------------
@@ -4726,7 +4794,7 @@ to I/O ports.
------------------------------------
:Capability: KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
-:Architectures: x86, arm, arm64, mips
+:Architectures: x86, arm64, mips
:Type: vm ioctl
:Parameters: struct kvm_clear_dirty_log (in)
:Returns: 0 on success, -1 on error
@@ -4838,7 +4906,7 @@ version has the following quirks:
4.119 KVM_ARM_VCPU_FINALIZE
---------------------------
-:Architectures: arm, arm64
+:Architectures: arm64
:Type: vcpu ioctl
:Parameters: int feature (in)
:Returns: 0 on success, -1 on error
@@ -5920,7 +5988,7 @@ should put the acknowledged interrupt vector into the 'epr' field.
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
+or some special instruction). In case of 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.
@@ -5939,6 +6007,11 @@ Valid values for 'type' are:
to ignore the request, or to gather VM memory core dump and/or
reset/shutdown of the VM.
+Valid flags are:
+
+ - KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2 (arm64 only) -- the guest issued
+ a SYSTEM_RESET2 call according to v1.1 of the PSCI specification.
+
::
/* KVM_EXIT_IOAPIC_EOI */
@@ -6013,7 +6086,7 @@ in send_page or recv a buffer to recv_page).
__u64 fault_ipa;
} arm_nisv;
-Used on arm and arm64 systems. If a guest accesses memory not in a memslot,
+Used on arm64 systems. If a guest accesses memory not in a memslot,
KVM will typically return to userspace and ask it to do MMIO emulation on its
behalf. However, for certain classes of instructions, no instruction decode
(direction, length of memory access) is provided, and fetching and decoding
@@ -6030,11 +6103,10 @@ did not fall within an I/O window.
Userspace implementations can query for KVM_CAP_ARM_NISV_TO_USER, and enable
this capability at VM creation. Once this is done, these types of errors will
instead return to userspace with KVM_EXIT_ARM_NISV, with the valid bits from
-the HSR (arm) and ESR_EL2 (arm64) in the esr_iss field, and the faulting IPA
-in the fault_ipa field. Userspace can either fix up the access if it's
-actually an I/O access by decoding the instruction from guest memory (if it's
-very brave) and continue executing the guest, or it can decide to suspend,
-dump, or restart the guest.
+the ESR_EL2 in the esr_iss field, and the faulting IPA in the fault_ipa field.
+Userspace can either fix up the access if it's actually an I/O access by
+decoding the instruction from guest memory (if it's very brave) and continue
+executing the guest, or it can decide to suspend, dump, or restart the guest.
Note that KVM does not skip the faulting instruction as it does for
KVM_EXIT_MMIO, but userspace has to emulate any change to the processing state
@@ -6741,7 +6813,7 @@ and injected exceptions.
7.18 KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
-:Architectures: x86, arm, arm64, mips
+:Architectures: x86, arm64, mips
:Parameters: args[0] whether feature should be enabled or not
Valid flags are::
@@ -7011,6 +7083,56 @@ resource that is controlled with the H_SET_MODE hypercall.
This capability allows a guest kernel to use a better-performance mode for
handling interrupts and system calls.
+7.31 KVM_CAP_DISABLE_QUIRKS2
+----------------------------
+
+:Capability: KVM_CAP_DISABLE_QUIRKS2
+:Parameters: args[0] - set of KVM quirks to disable
+:Architectures: x86
+:Type: vm
+
+This capability, if enabled, will cause KVM to disable some behavior
+quirks.
+
+Calling KVM_CHECK_EXTENSION for this capability returns a bitmask of
+quirks that can be disabled in KVM.
+
+The argument to KVM_ENABLE_CAP for this capability is a bitmask of
+quirks to disable, and must be a subset of the bitmask returned by
+KVM_CHECK_EXTENSION.
+
+The valid bits in cap.args[0] are:
+
+=================================== ============================================
+ KVM_X86_QUIRK_LINT0_REENABLED By default, the reset value for the LVT
+ LINT0 register is 0x700 (APIC_MODE_EXTINT).
+ When this quirk is disabled, the reset value
+ is 0x10000 (APIC_LVT_MASKED).
+
+ KVM_X86_QUIRK_CD_NW_CLEARED By default, KVM clears CR0.CD and CR0.NW.
+ When this quirk is disabled, KVM does not
+ change the value of CR0.CD and CR0.NW.
+
+ KVM_X86_QUIRK_LAPIC_MMIO_HOLE By default, the MMIO LAPIC interface is
+ available even when configured for x2APIC
+ mode. When this quirk is disabled, KVM
+ disables the MMIO LAPIC interface if the
+ LAPIC is in x2APIC mode.
+
+ KVM_X86_QUIRK_OUT_7E_INC_RIP By default, KVM pre-increments %rip before
+ exiting to userspace for an OUT instruction
+ to port 0x7e. When this quirk is disabled,
+ KVM does not pre-increment %rip before
+ exiting to userspace.
+
+ KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT When this quirk is disabled, KVM sets
+ CPUID.01H:ECX[bit 3] (MONITOR/MWAIT) if
+ IA32_MISC_ENABLE[bit 18] (MWAIT) is set.
+ Additionally, when this quirk is disabled,
+ KVM clears CPUID.01H:ECX[bit 3] if
+ IA32_MISC_ENABLE[bit 18] is cleared.
+=================================== ============================================
+
8. Other capabilities.
======================
@@ -7138,7 +7260,7 @@ reserved.
8.9 KVM_CAP_ARM_USER_IRQ
------------------------
-:Architectures: arm, arm64
+:Architectures: 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
@@ -7265,7 +7387,7 @@ HvFlushVirtualAddressList, HvFlushVirtualAddressListEx.
8.19 KVM_CAP_ARM_INJECT_SERROR_ESR
----------------------------------
-:Architectures: arm, arm64
+:Architectures: arm64
This capability indicates that userspace can specify (via the
KVM_SET_VCPU_EVENTS ioctl) the syndrome value reported to the guest when it
@@ -7575,3 +7697,25 @@ The argument to KVM_ENABLE_CAP is also a bitmask, and must be a subset
of the result of KVM_CHECK_EXTENSION. KVM will forward to userspace
the hypercalls whose corresponding bit is in the argument, and return
ENOSYS for the others.
+
+8.35 KVM_CAP_PMU_CAPABILITY
+---------------------------
+
+:Capability KVM_CAP_PMU_CAPABILITY
+:Architectures: x86
+:Type: vm
+:Parameters: arg[0] is bitmask of PMU virtualization capabilities.
+:Returns 0 on success, -EINVAL when arg[0] contains invalid bits
+
+This capability alters PMU virtualization in KVM.
+
+Calling KVM_CHECK_EXTENSION for this capability returns a bitmask of
+PMU virtualization capabilities that can be adjusted on a VM.
+
+The argument to KVM_ENABLE_CAP is also a bitmask and selects specific
+PMU virtualization capabilities to be applied to the VM. This can
+only be invoked on a VM prior to the creation of VCPUs.
+
+At this time, KVM_PMU_CAP_DISABLE is the only capability. Setting
+this capability will disable PMU virtualization for that VM. Usermode
+should adjust CPUID leaf 0xA to reflect that the PMU is disabled.