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KVM: Lazify fpu activation and deactivation

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Defer fpu deactivation as much as possible - if the guest fpu is loaded, keep
it loaded until the next heavyweight exit (where we are forced to unload it).
This reduces unnecessary exits.

We also defer fpu activation on clts; while clts signals the intent to use the
fpu, we can't be sure the guest will actually use it.

Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Avi Kivity
2009-12-30 12:40:26 +02:00
committed by Marcelo Tosatti
parent e8467fda83
commit 02daab21d9
5 changed files with 38 additions and 31 deletions
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7
arch/x86/kvm/x86.c
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@@ -1509,8 +1509,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
kvm_x86_ops->vcpu_put(vcpu);
kvm_put_guest_fpu(vcpu);
kvm_x86_ops->vcpu_put(vcpu);
}
static int is_efer_nx(void)
@@ -4006,6 +4006,10 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
r = 0;
goto out;
}
if (test_and_clear_bit(KVM_REQ_DEACTIVATE_FPU, &vcpu->requests)) {
vcpu->fpu_active = 0;
kvm_x86_ops->fpu_deactivate(vcpu);
}
}
preempt_disable();
@@ -5075,6 +5079,7 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
kvm_fx_save(&vcpu->arch.guest_fx_image);
kvm_fx_restore(&vcpu->arch.host_fx_image);
++vcpu->stat.fpu_reload;
set_bit(KVM_REQ_DEACTIVATE_FPU, &vcpu->requests);
}
EXPORT_SYMBOL_GPL(kvm_put_guest_fpu);