diff options
| author | Jim Mattson | 2018-12-06 00:28:59 +0100 |
|---|---|---|
| committer | Paolo Bonzini | 2018-12-14 17:59:48 +0100 |
| commit | 898a811f1486df3209ce857027d0564d6a616cf2 (patch) | |
| tree | a60697326daf78c1a8d8af20433f86c541352747 /arch/x86/kvm/vmx/vmx.c | |
| parent | kvm: vmx: Set IA32_TSC_AUX for legacy mode guests (diff) | |
| download | kernel-qcow2-linux-898a811f1486df3209ce857027d0564d6a616cf2.tar.gz kernel-qcow2-linux-898a811f1486df3209ce857027d0564d6a616cf2.tar.xz kernel-qcow2-linux-898a811f1486df3209ce857027d0564d6a616cf2.zip | |
kvm: vmx: Document the need for MSR_STAR in i386 builds
Add a comment explaining why MSR_STAR must be included in
vmx_msr_index[] even for i386 builds.
The elided comment has not been relevant since move_msr_up() was
introduced in commit a75beee6e4f5d ("KVM: VMX: Avoid saving and
restoring msrs on lightweight vmexit").
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx/vmx.c')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index c1feb62faac4..d754fd0c8674 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -373,8 +373,11 @@ static const struct kvm_vmx_segment_field { u64 host_efer; /* - * Keep MSR_STAR at the end, as setup_msrs() will try to optimize it - * away by decrementing the array size. + * Though SYSCALL is only supported in 64-bit mode on Intel CPUs, kvm + * will emulate SYSCALL in legacy mode if the vendor string in guest + * CPUID.0:{EBX,ECX,EDX} is "AuthenticAMD" or "AMDisbetter!" To + * support this emulation, IA32_STAR must always be included in + * vmx_msr_index[], even in i386 builds. */ const u32 vmx_msr_index[] = { #ifdef CONFIG_X86_64 |