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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 a75beee6e4 ("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>
This commit is contained in:
Jim Mattson 2018-12-05 15:28:59 -08:00 committed by Paolo Bonzini
parent 0023ef39dc
commit 898a811f14
1 changed files with 5 additions and 2 deletions
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7
arch/x86/kvm/vmx/vmx.c
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@ -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