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Diffstat (limited to 'Documentation/virtual/kvm/nested-vmx.txt')
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diff --git a/Documentation/virtual/kvm/nested-vmx.txt b/Documentation/virtual/kvm/nested-vmx.txt deleted file mode 100644 index 97eb1353e962..000000000000 --- a/Documentation/virtual/kvm/nested-vmx.txt +++ /dev/null @@ -1,240 +0,0 @@ -Nested VMX -========== - -Overview ---------- - -On Intel processors, KVM uses Intel's VMX (Virtual-Machine eXtensions) -to easily and efficiently run guest operating systems. Normally, these guests -*cannot* themselves be hypervisors running their own guests, because in VMX, -guests cannot use VMX instructions. - -The "Nested VMX" feature adds this missing capability - of running guest -hypervisors (which use VMX) with their own nested guests. It does so by -allowing a guest to use VMX instructions, and correctly and efficiently -emulating them using the single level of VMX available in the hardware. - -We describe in much greater detail the theory behind the nested VMX feature, -its implementation and its performance characteristics, in the OSDI 2010 paper -"The Turtles Project: Design and Implementation of Nested Virtualization", -available at: - - http://www.usenix.org/events/osdi10/tech/full_papers/Ben-Yehuda.pdf - - -Terminology ------------ - -Single-level virtualization has two levels - the host (KVM) and the guests. -In nested virtualization, we have three levels: The host (KVM), which we call -L0, the guest hypervisor, which we call L1, and its nested guest, which we -call L2. - - -Running nested VMX ------------------- - -The nested VMX feature is disabled by default. It can be enabled by giving -the "nested=1" option to the kvm-intel module. - -No modifications are required to user space (qemu). However, qemu's default -emulated CPU type (qemu64) does not list the "VMX" CPU feature, so it must be -explicitly enabled, by giving qemu one of the following options: - - -cpu host (emulated CPU has all features of the real CPU) - - -cpu qemu64,+vmx (add just the vmx feature to a named CPU type) - - -ABIs ----- - -Nested VMX aims to present a standard and (eventually) fully-functional VMX -implementation for the a guest hypervisor to use. As such, the official -specification of the ABI that it provides is Intel's VMX specification, -namely volume 3B of their "Intel 64 and IA-32 Architectures Software -Developer's Manual". Not all of VMX's features are currently fully supported, -but the goal is to eventually support them all, starting with the VMX features -which are used in practice by popular hypervisors (KVM and others). - -As a VMX implementation, nested VMX presents a VMCS structure to L1. -As mandated by the spec, other than the two fields revision_id and abort, -this structure is *opaque* to its user, who is not supposed to know or care -about its internal structure. Rather, the structure is accessed through the -VMREAD and VMWRITE instructions. -Still, for debugging purposes, KVM developers might be interested to know the -internals of this structure; This is struct vmcs12 from arch/x86/kvm/vmx.c. - -The name "vmcs12" refers to the VMCS that L1 builds for L2. In the code we -also have "vmcs01", the VMCS that L0 built for L1, and "vmcs02" is the VMCS -which L0 builds to actually run L2 - how this is done is explained in the -aforementioned paper. - -For convenience, we repeat the content of struct vmcs12 here. If the internals -of this structure changes, this can break live migration across KVM versions. -VMCS12_REVISION (from vmx.c) should be changed if struct vmcs12 or its inner -struct shadow_vmcs is ever changed. - - typedef u64 natural_width; - struct __packed vmcs12 { - /* According to the Intel spec, a VMCS region must start with - * these two user-visible fields */ - u32 revision_id; - u32 abort; - - u32 launch_state; /* set to 0 by VMCLEAR, to 1 by VMLAUNCH */ - u32 padding[7]; /* room for future expansion */ - - u64 io_bitmap_a; - u64 io_bitmap_b; - u64 msr_bitmap; - u64 vm_exit_msr_store_addr; - u64 vm_exit_msr_load_addr; - u64 vm_entry_msr_load_addr; - u64 tsc_offset; - u64 virtual_apic_page_addr; - u64 apic_access_addr; - u64 ept_pointer; - u64 guest_physical_address; - u64 vmcs_link_pointer; - u64 guest_ia32_debugctl; - u64 guest_ia32_pat; - u64 guest_ia32_efer; - u64 guest_pdptr0; - u64 guest_pdptr1; - u64 guest_pdptr2; - u64 guest_pdptr3; - u64 host_ia32_pat; - u64 host_ia32_efer; - u64 padding64[8]; /* room for future expansion */ - natural_width cr0_guest_host_mask; - natural_width cr4_guest_host_mask; - natural_width cr0_read_shadow; - natural_width cr4_read_shadow; - natural_width cr3_target_value0; - natural_width cr3_target_value1; - natural_width cr3_target_value2; - natural_width cr3_target_value3; - natural_width exit_qualification; - natural_width guest_linear_address; - natural_width guest_cr0; - natural_width guest_cr3; - natural_width guest_cr4; - natural_width guest_es_base; - natural_width guest_cs_base; - natural_width guest_ss_base; - natural_width guest_ds_base; - natural_width guest_fs_base; - natural_width guest_gs_base; - natural_width guest_ldtr_base; - natural_width guest_tr_base; - natural_width guest_gdtr_base; - natural_width guest_idtr_base; - natural_width guest_dr7; - natural_width guest_rsp; - natural_width guest_rip; - natural_width guest_rflags; - natural_width guest_pending_dbg_exceptions; - natural_width guest_sysenter_esp; - natural_width guest_sysenter_eip; - natural_width host_cr0; - natural_width host_cr3; - natural_width host_cr4; - natural_width host_fs_base; - natural_width host_gs_base; - natural_width host_tr_base; - natural_width host_gdtr_base; - natural_width host_idtr_base; - natural_width host_ia32_sysenter_esp; - natural_width host_ia32_sysenter_eip; - natural_width host_rsp; - natural_width host_rip; - natural_width paddingl[8]; /* room for future expansion */ - u32 pin_based_vm_exec_control; - u32 cpu_based_vm_exec_control; - u32 exception_bitmap; - u32 page_fault_error_code_mask; - u32 page_fault_error_code_match; - u32 cr3_target_count; - u32 vm_exit_controls; - u32 vm_exit_msr_store_count; - u32 vm_exit_msr_load_count; - u32 vm_entry_controls; - u32 vm_entry_msr_load_count; - u32 vm_entry_intr_info_field; - u32 vm_entry_exception_error_code; - u32 vm_entry_instruction_len; - u32 tpr_threshold; - u32 secondary_vm_exec_control; - u32 vm_instruction_error; - u32 vm_exit_reason; - u32 vm_exit_intr_info; - u32 vm_exit_intr_error_code; - u32 idt_vectoring_info_field; - u32 idt_vectoring_error_code; - u32 vm_exit_instruction_len; - u32 vmx_instruction_info; - u32 guest_es_limit; - u32 guest_cs_limit; - u32 guest_ss_limit; - u32 guest_ds_limit; - u32 guest_fs_limit; - u32 guest_gs_limit; - u32 guest_ldtr_limit; - u32 guest_tr_limit; - u32 guest_gdtr_limit; - u32 guest_idtr_limit; - u32 guest_es_ar_bytes; - u32 guest_cs_ar_bytes; - u32 guest_ss_ar_bytes; - u32 guest_ds_ar_bytes; - u32 guest_fs_ar_bytes; - u32 guest_gs_ar_bytes; - u32 guest_ldtr_ar_bytes; - u32 guest_tr_ar_bytes; - u32 guest_interruptibility_info; - u32 guest_activity_state; - u32 guest_sysenter_cs; - u32 host_ia32_sysenter_cs; - u32 padding32[8]; /* room for future expansion */ - u16 virtual_processor_id; - u16 guest_es_selector; - u16 guest_cs_selector; - u16 guest_ss_selector; - u16 guest_ds_selector; - u16 guest_fs_selector; - u16 guest_gs_selector; - u16 guest_ldtr_selector; - u16 guest_tr_selector; - u16 host_es_selector; - u16 host_cs_selector; - u16 host_ss_selector; - u16 host_ds_selector; - u16 host_fs_selector; - u16 host_gs_selector; - u16 host_tr_selector; - }; - - -Authors -------- - -These patches were written by: - Abel Gordon, abelg <at> il.ibm.com - Nadav Har'El, nyh <at> il.ibm.com - Orit Wasserman, oritw <at> il.ibm.com - Ben-Ami Yassor, benami <at> il.ibm.com - Muli Ben-Yehuda, muli <at> il.ibm.com - -With contributions by: - Anthony Liguori, aliguori <at> us.ibm.com - Mike Day, mdday <at> us.ibm.com - Michael Factor, factor <at> il.ibm.com - Zvi Dubitzky, dubi <at> il.ibm.com - -And valuable reviews by: - Avi Kivity, avi <at> redhat.com - Gleb Natapov, gleb <at> redhat.com - Marcelo Tosatti, mtosatti <at> redhat.com - Kevin Tian, kevin.tian <at> intel.com - and others. |