> -----Original Message-----
> From: Avi Kivity [mailto:[email protected]]
> Sent: Monday, September 10, 2012 4:07 PM
> To: Hao, Xudong
> Cc: [email protected]; Zhang, Xiantao; [email protected]
> Subject: Re: [PATCH v2] kvm/fpu: Enable fully eager restore kvm FPU
>
> >
> > Avi, I'm not sure if I fully understand of you. Do you mean enter guest
> > with a
> fpu_active=0 and then fpu does not restore?
>
> Yes.
>
> > If so, I will add fpu_active=1 in the no-lazy case.
> >
> > - kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
> > + if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&
> > + (vcpu->arch.xcr0 & ~((u64)KVM_XSTATE_LAZY))) {
> > + kvm_x86_ops->fpu_activate(vcpu);
> > + vcpu->fpu_active=1;
> > + }
> > + else
> > + kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
> >
>
> It doesn't help here.
>
> 1 guest boot
> 2 kvm_userspace_exit (deactivates fpu)
> 3 XSETBV exit that sets xcr0.new_bit
> 4 kvm_enter
>
> There is no call to kvm_put_guest_fpu() between 3 and 4, you need
> something in __kvm_set_xcr() to activate the fpu.
>
Yes, it's code path when enable xsave in guest, I'll add fpu activate there and
remain v2 patch in kvm_put_guest_fpu().
@@ -554,6 +554,8 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
xcr0 = xcr;
if (kvm_x86_ops->get_cpl(vcpu) != 0)
return 1;
+ if (xcr0 & ~((u64)KVM_XSTATE_LAZY))
+ kvm_x86_ops->fpu_activate(vcpu);
if (!(xcr0 & XSTATE_FP))
return 1;
if ((xcr0 & XSTATE_YMM) && !(xcr0 & XSTATE_SSE))
> Note you also need to consider writes to xcr0 and cr4 that happen in the
> reverse order due to live migration.
>
I'm confused of this, doesn't setting cr4 firstly then xcr0?
Do you mean current live migration has a reverse order, or it must be a reverse
order with my eager restore patch?
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