> -----Original Message-----
> From: Avi Kivity [mailto:a...@redhat.com]
> Sent: Wednesday, September 19, 2012 6:24 PM
> To: Hao, Xudong
> Cc: Marcelo Tosatti; kvm@vger.kernel.org; Zhang, Xiantao
> Subject: Re: [PATCH v3] kvm/fpu: Enable fully eager restore kvm FPU
> > That may be:
> >
> > static bool lazy_fpu_allowed()
> > {
> > return !(vcpu->arch.xcr0 & ~((u64)KVM_XSTATE_LAZY));
> > }
>
> Shouldn't it depend on cr4.osxsave as well?
>
It do need to check cr4.osxsave due to a separate function.
static bool lazy_fpu_allowed(struct kvm_vcpu *vcpu)
{
return !kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) ||
!(vcpu->arch.xcr0 & ~((u64)KVM_XSTATE_LAZY));
}
> >
> >> On guest entry:
> >> if (!lazy_fpu_allowed(vcpu))
> >> kvm_x86_ops->fpu_activate(vcpu);
> >
>
> But we already have that:
>
> if (vcpu->fpu_active)
> kvm_load_guest_fpu(vcpu);
>
> so why not manage fpu_active to be always set when needed? I don't want
> more checks in the entry path.
>
I means add fpu_active() in kvm_set_xcr(), not in guest entry. Then the
fpu_active will be set always when guest initialize xstate.
@@ -574,6 +574,9 @@ int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
kvm_inject_gp(vcpu, 0);
return 1;
}
+ if (!lazy_fpu_allowed(vcpu))
+ kvm_x86_ops->fpu_activate(vcpu);
return 0;
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