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 11:59:46 -0300 Message-ID: <20110920145946.GA28219@amt.cnet> References: <1316515394-24762-1-git-send-email-avi@redhat.com> <20110920132537.GA27075@amt.cnet> <4E789B72.2050904@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]:56568 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751723Ab1ITPAO (ORCPT ); Tue, 20 Sep 2011 11:00:14 -0400 Content-Disposition: inline In-Reply-To: <4E789B72.2050904@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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. > 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). > > > >> @@ -2864,6 +2866,7 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu, > >> | KVM_VCPUEVENT_VALID_SHADOW)) > >> return -EINVAL; > >> > >> + process_nmi(vcpu); > > > >This should be after nmi fields are set, not before? > > > > It's actually to clear queued NMIs in case we set nmi_pending (which > should never happen unless the machine is completely quiet, since > it's asynchronous to the vcpu; same as the IRR). OK.