On 09/11/2012 09:43 AM, Hao, Xudong wrote: >> -----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? I mean I want the code to work regardless of whether KVM_SET_SREGS or KVM_SET_XCRS is called first. -- error compiling committee.c: too many arguments to function -- 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
