KVM: VMX: Cache IA32_DEBUGCTL in memory
MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT, so it is saved/restored each time during world switch. This patch caches the host IA32_DEBUGCTL MSR and saves/restores the host IA32_DEBUGCTL msr when guest/host switches to avoid to save/restore each time during world switch. This saves about 100 clock cycles per vmexit. Suggested-by: NJim Mattson <jmattson@google.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Jim Mattson <jmattson@google.com> Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com> Reviewed-by: NJim Mattson <jmattson@google.com> Reviewed-by: NDavid Hildenbrand <david@redhat.com> Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
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