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Commit 7807fa6c authored by Anthony Liguori's avatar Anthony Liguori Committed by Avi Kivity
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KVM: Lazy FPU support for SVM 



Avoid saving and restoring the guest fpu state on every exit.  This
shaves ~100 cycles off the guest/host switch.

Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 4c690a1e

drivers/kvm/kvm.h

+2 −0
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ 
#define FX_BUF_SIZE (2 * FX_IMAGE_SIZE + FX_IMAGE_ALIGN)



#define DE_VECTOR 0

#define NM_VECTOR 7

#define DF_VECTOR 8

#define TS_VECTOR 10

#define NP_VECTOR 11
@@ -301,6 +302,7 @@ struct kvm_vcpu { 
	char fx_buf[FX_BUF_SIZE];

	char *host_fx_image;

	char *guest_fx_image;

	int fpu_active;



	int mmio_needed;

	int mmio_read_completed;

drivers/kvm/svm.c

+31 −4
Original line number Diff line number Diff line
@@ -587,6 +587,7 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu) 
	init_vmcb(vcpu->svm->vmcb);



	fx_init(vcpu);

	vcpu->fpu_active = 1;

	vcpu->apic_base = 0xfee00000 |

			/*for vcpu 0*/ MSR_IA32_APICBASE_BSP |

			MSR_IA32_APICBASE_ENABLE;
@@ -756,6 +757,11 @@ static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) 
		}

	}

#endif

	if ((vcpu->cr0 & CR0_TS_MASK) && !(cr0 & CR0_TS_MASK)) {

		vcpu->svm->vmcb->control.intercept_exceptions &= ~(1 << NM_VECTOR);

		vcpu->fpu_active = 1;

	}



	vcpu->cr0 = cr0;

	cr0 |= CR0_PG_MASK | CR0_WP_MASK;

	cr0 &= ~(CR0_CD_MASK | CR0_NW_MASK);
@@ -928,6 +934,16 @@ static int pf_interception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) 
	return 0;

}



static int nm_interception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)

{

       vcpu->svm->vmcb->control.intercept_exceptions &= ~(1 << NM_VECTOR);

       if (!(vcpu->cr0 & CR0_TS_MASK))

               vcpu->svm->vmcb->save.cr0 &= ~CR0_TS_MASK;

       vcpu->fpu_active = 1;



       return 1;

}



static int shutdown_interception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)

{

	/*
@@ -1292,6 +1308,7 @@ static int (*svm_exit_handlers[])(struct kvm_vcpu *vcpu, 
	[SVM_EXIT_WRITE_DR5]			= emulate_on_interception,

	[SVM_EXIT_WRITE_DR7]			= emulate_on_interception,

	[SVM_EXIT_EXCP_BASE + PF_VECTOR] 	= pf_interception,

	[SVM_EXIT_EXCP_BASE + NM_VECTOR] 	= nm_interception,

	[SVM_EXIT_INTR] 			= nop_on_interception,

	[SVM_EXIT_NMI]				= nop_on_interception,

	[SVM_EXIT_SMI]				= nop_on_interception,
@@ -1481,8 +1498,10 @@ static int svm_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) 
		load_db_regs(vcpu->svm->db_regs);

	}



	if (vcpu->fpu_active) {

		fx_save(vcpu->host_fx_image);

		fx_restore(vcpu->guest_fx_image);

	}



	asm volatile (

#ifdef CONFIG_X86_64
@@ -1593,8 +1612,10 @@ static int svm_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) 
#endif

		: "cc", "memory" );



	if (vcpu->fpu_active) {

		fx_save(vcpu->guest_fx_image);

		fx_restore(vcpu->host_fx_image);

	}



	if ((vcpu->svm->vmcb->save.dr7 & 0xff))

		load_db_regs(vcpu->svm->host_db_regs);
@@ -1664,6 +1685,12 @@ static void svm_set_cr3(struct kvm_vcpu *vcpu, unsigned long root) 
{

	vcpu->svm->vmcb->save.cr3 = root;

	force_new_asid(vcpu);



	if (vcpu->fpu_active) {

		vcpu->svm->vmcb->control.intercept_exceptions |= (1 << NM_VECTOR);

		vcpu->svm->vmcb->save.cr0 |= CR0_TS_MASK;

		vcpu->fpu_active = 0;

	}

}



static void svm_inject_page_fault(struct kvm_vcpu *vcpu,