> On Nov 6, 2014, at 11:44, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > > > On 06/11/2014 10:13, Nadav Amit wrote: >> >>> On Nov 6, 2014, at 10:58, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >>> >>> On 05/11/2014 21:31, Nadav Amit wrote: >>>> You are correct, it does not appear clearly in the SDM, but that is what real hardware does. >>>> If you look at bochs - http://code.metager.de/source/xref/bochs/bochs/cpu/init.cc - you’ll see they call >>>> "BX_CPU_THIS_PTR xcr0.set32(0x1);” regardless to whether it is hardware or software reset (the latter happens on INIT). >>> >>> Fair enough. :) >> Thanks. It is turning harder to find references for the crazy x86 behaviour. :) > > Indeed, I'll ask Intel to clarify this one too. > > The crazy thing is that AMD doesn't say anything, either! Their own > manual just says "Hardware initializes XCR0 to 0000_0000_0000_0001h", > but it doesn't say when. I know. I looked at their manual too. > >>> Does the patch in >>> http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/129060 look good? >> >> Yes. However, re-reviewing the patches both my patch and yours actually do something slightly different than the spec: they clear XMM8-15 and YMM[128:…] which should not happen on INIT according to the spec. > > Yes, my patch just wanted to have the same effect as yours, but > fpu_finit must remain in fx_alloc. Setting cr0 is also unnecessary, > since vmx_vcpu_reset and svm_vcpu_reset both do this. > >> Fixing it might be a bit intrusive. What do you say? > > I think it's easy if we start with my version of the change: > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index dc932d388c43..aba13df4e0ec 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -915,8 +915,6 @@ void kvm_pic_clear_all(struct kvm_pic *pic, int irq_source_id); > > void kvm_inject_nmi(struct kvm_vcpu *vcpu); > > -int fx_init(struct kvm_vcpu *vcpu); > - > void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, > const u8 *new, int bytes); > int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn); > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index e0260ccd78a4..0ef4c0b27248 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -6868,7 +6868,7 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu) > return 0; > } > > -int fx_init(struct kvm_vcpu *vcpu) > +static int fx_init(struct kvm_vcpu *vcpu) > { > int err; > > @@ -6878,16 +6878,8 @@ int fx_init(struct kvm_vcpu *vcpu) > > fpu_finit(&vcpu->arch.guest_fpu); > > - /* > - * Ensure guest xcr0 is valid for loading > - */ > - vcpu->arch.xcr0 = XSTATE_FP; > - > - vcpu->arch.cr0 |= X86_CR0_ET; I think this line was removed by mistake. > - > return 0; > } > -EXPORT_SYMBOL_GPL(fx_init); > > static void fx_free(struct kvm_vcpu *vcpu) > { > @@ -7025,6 +7017,11 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu) > vcpu->arch.regs_avail = ~0; > vcpu->arch.regs_dirty = ~0; > > + /* > + * Ensure guest xcr0 is valid for loading > + */ > + vcpu->arch.xcr0 = XSTATE_FP; > + > kvm_x86_ops->vcpu_reset(vcpu); > } > I’ll give it a shot (in a couple of weeks). Thanks, Nadav -- 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
