> -----Original Message----- > From: Avi Kivity [mailto:avi@xxxxxxxxxx] > Sent: Monday, September 10, 2012 4:07 PM > To: Hao, Xudong > Cc: kvm@xxxxxxxxxxxxxxx; Zhang, Xiantao; Joerg.Roedel@xxxxxxx > 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? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
