Commit 74c55931 authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini
Browse files

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: default avatarJim 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: default avatarWanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent 276c796c

arch/x86/kvm/vmx.c

+6 −4
Original line number Diff line number Diff line
@@ -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

	/*

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