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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: Jim 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: Wanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Wanpeng Li 2017-11-29 01:31:20 -08:00 committed by Paolo Bonzini
parent 276c796cfe
commit 74c55931c7
1 changed files with 6 additions and 4 deletions
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10
arch/x86/kvm/vmx.c
View File

@ -650,6 +650,8 @@ struct vcpu_vmx {
u32 host_pkru;
unsigned long host_debugctlmsr;
/*
* Only bits masked by msr_ia32_feature_control_valid_bits can be set in
* msr_ia32_feature_control. FEATURE_CONTROL_LOCKED is always included
@ -2318,6 +2320,7 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
vmx_vcpu_pi_load(vcpu, cpu);
vmx->host_pkru = read_pkru();
vmx->host_debugctlmsr = get_debugctlmsr();
}
static void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu)
@ -9261,7 +9264,7 @@ static void vmx_arm_hv_timer(struct kvm_vcpu *vcpu)
static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
unsigned long debugctlmsr, cr3, cr4;
unsigned long cr3, cr4;
/* Record the guest's net vcpu time for enforced NMI injections. */
if (unlikely(!enable_vnmi &&
@ -9314,7 +9317,6 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
__write_pkru(vcpu->arch.pkru);
atomic_switch_perf_msrs(vmx);
debugctlmsr = get_debugctlmsr();
vmx_arm_hv_timer(vcpu);
@ -9425,8 +9427,8 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
);
/* MSR_IA32_DEBUGCTLMSR is zeroed on vmexit. Restore it if needed */
if (debugctlmsr)
update_debugctlmsr(debugctlmsr);
if (vmx->host_debugctlmsr)
update_debugctlmsr(vmx->host_debugctlmsr);
#ifndef CONFIG_X86_64
/*