x86/kvm: use Enlightened VMCS when running on Hyper-V

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Enlightened VMCS is just a structure in memory, the main benefit
besides avoiding somewhat slower VMREAD/VMWRITE is using clean field
mask: we tell the underlying hypervisor which fields were modified
since VMEXIT so there's no need to inspect them all.

Tight CPUID loop test shows significant speedup:
Before: 18890 cycles
After: 8304 cycles

Static key is being used to avoid performance penalty for non-Hyper-V
deployments.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

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This commit is contained in:

Vitaly Kuznetsov 2018-03-20 15:02:11 +01:00 • committed by Radim Krčmář

parent 5431390b30

commit 773e8a0425

2 changed files with 615 additions and 10 deletions

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301

arch/x86/kvm/vmx.c

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324

arch/x86/kvm/vmx_evmcs.h

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