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. >> 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; - 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); } -- 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
