From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH v2] KVM: Fix simultaneous NMIs Date: Tue, 20 Sep 2011 13:30:21 -0300 Message-ID: <20110920163021.GA29618@amt.cnet> References: <1316515394-24762-1-git-send-email-avi@redhat.com> <20110920132537.GA27075@amt.cnet> <4E789B72.2050904@redhat.com> <20110920145946.GA28219@amt.cnet> <4E78BE21.4070508@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org, Jan Kiszka To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:22156 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751499Ab1ITQat (ORCPT ); Tue, 20 Sep 2011 12:30:49 -0400 Content-Disposition: inline In-Reply-To: <4E78BE21.4070508@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Sep 20, 2011 at 07:24:01PM +0300, Avi Kivity wrote: > On 09/20/2011 05:59 PM, Marcelo Tosatti wrote: > >On Tue, Sep 20, 2011 at 04:56:02PM +0300, Avi Kivity wrote: > >> On 09/20/2011 04:25 PM, Marcelo Tosatti wrote: > >> >> > >> >> @@ -2827,6 +2828,7 @@ static int kvm_vcpu_ioctl_x86_set_mce(struct kvm_vcpu *vcpu, > >> >> static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu, > >> >> struct kvm_vcpu_events *events) > >> >> { > >> >> + process_nmi(vcpu); > >> >> events->exception.injected = > >> >> vcpu->arch.exception.pending&& > >> >> !kvm_exception_is_soft(vcpu->arch.exception.nr); > >> >> @@ -2844,7 +2846,7 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu, > >> >> KVM_X86_SHADOW_INT_MOV_SS | KVM_X86_SHADOW_INT_STI); > >> >> > >> >> events->nmi.injected = vcpu->arch.nmi_injected; > >> >> - events->nmi.pending = vcpu->arch.nmi_pending; > >> >> + events->nmi.pending = vcpu->arch.nmi_pending != 0; > >> >> events->nmi.masked = kvm_x86_ops->get_nmi_mask(vcpu); > >> >> events->nmi.pad = 0; > >> > > >> >nmi_queued should also be saved and restored. Not sure if its necessary > >> >though. > >> > > >> >Should at least reset nmi_queued somewhere (set_vcpu_events?). > >> > >> Did you miss the call to process_nmi()? > > > >It transfers nmi_queued to nmi_pending with capping. What i mean is that > >upon system reset, nmi_queued (which refers to pre-reset system state) > >should be zeroed. > > The is get_events(); for set_events(), process_nmi() does zero > nmi_queued() (and then we overwrite nmi_pending). Right. > > > >> We do have a small issue. If we exit during NMI-blocked-by-STI and > >> nmi_pending == 2, then we lose the second interrupt. Should rarely > >> happen, since external interrupts never exit in that condition, but > >> it's a wart. > > > >And the above system reset case, you should be able to handle it by > >saving/restoring nmi_queued (so that QEMU can zero it in vcpu_reset). > > We could just add a KVM_CAP (and flag) that extends nmi_pending from > a bool to a counter. Or just add a new field to the pad.