On Thu, Mar 24, 2011 at 03:27:16PM +0200, Gleb Natapov wrote: > On Thu, Mar 24, 2011 at 09:47:00AM -0300, Marcelo Tosatti wrote: > > > > Since "Fix race between nmi injection and enabling nmi window", pending NMI > > can be represented in KVM_REQ_NMI vcpu->requests bit. > > > > When setting vcpu state via SET_VCPU_EVENTS, for example during reset, > > the REQ_NMI bit should be cleared otherwise pending NMI is transferred > > to nmi_pending upon vcpu entry. > > > > Also should consider requests bit on runnable conditional. > > > > BZ: http://bugzilla.redhat.com/show_bug.cgi?id=684719 > > > Looks like we need to clear request bit on cpu reset too. KVM_REQ_NMI > start to become more complicated that it was initially. May be replaced > it with something like this: > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 1b8b16a..6a66d19 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -5151,6 +5151,7 @@ static void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu) > static int vcpu_enter_guest(struct kvm_vcpu *vcpu) > { > int r; > + int nmi_pending; > bool req_int_win = !irqchip_in_kernel(vcpu->kvm) && > vcpu->run->request_interrupt_window; > > @@ -5188,19 +5189,19 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) > r = 1; > goto out; > } > - if (kvm_check_request(KVM_REQ_NMI, vcpu)) > - vcpu->arch.nmi_pending = true; > } > > r = kvm_mmu_reload(vcpu); > if (unlikely(r)) > goto out; > + nmi_pending = vcpu->arch.nmi_pending; > + > if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) { Yep thats nicer. Race: remote CPU sets nmi_pending = true here, NMI injection not allowed, fails to open NMI window when it should. Unless i'm mistaken this should be rare enough to be irrelevant. Two patches one to revert REQ_NMI then another to fix the original problem makes backporting easier. -- 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
