From: Anthony Liguori <[email protected]>
Avoid saving and restoring the guest fpu state on every exit. This
shaves ~100 cycles off the guest/host switch.
Signed-off-by: Anthony Liguori <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>
---
drivers/kvm/kvm.h | 2 ++
drivers/kvm/svm.c | 35 +++++++++++++++++++++++++++++++----
2 files changed, 33 insertions(+), 4 deletions(-)
diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index d1a90c5..61ff085 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -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;
diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
index 644efc5..9438931 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -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 @@ again:
load_db_regs(vcpu->svm->db_regs);
}
- fx_save(vcpu->host_fx_image);
- fx_restore(vcpu->guest_fx_image);
+ 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 @@ again:
#endif
: "cc", "memory" );
- fx_save(vcpu->guest_fx_image);
- fx_restore(vcpu->host_fx_image);
+ 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,
--
1.5.0.6
-
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