From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH 5/5] KVM: arm/arm64: kvm_arch_vcpu_runnable: don't miss injected irqs Date: Sat, 14 Oct 2017 21:13:35 +0200 Message-ID: <20171014191335.GD1929@lvm> References: <20170929113041.24371-1-drjones@redhat.com> <20170929113041.24371-6-drjones@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 2157149D60 for ; Sat, 14 Oct 2017 15:12:48 -0400 (EDT) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id eYz90dTHdUau for ; Sat, 14 Oct 2017 15:12:47 -0400 (EDT) Received: from mail-wm0-f43.google.com (mail-wm0-f43.google.com [74.125.82.43]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 33DA249D3A for ; Sat, 14 Oct 2017 15:12:47 -0400 (EDT) Received: by mail-wm0-f43.google.com with SMTP id t69so26716338wmt.2 for ; Sat, 14 Oct 2017 12:13:37 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20170929113041.24371-6-drjones@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: Andrew Jones Cc: marc.zyngier@arm.com, kvmarm@lists.cs.columbia.edu List-Id: kvmarm@lists.cs.columbia.edu On Fri, Sep 29, 2017 at 01:30:41PM +0200, Andrew Jones wrote: > When the vPMU is in use if a VCPU's perf event overflow handler > were to fire after the VCPU started waiting, then the wake up > done by the kvm_vcpu_kick() call in the handler would do nothing, > as no "pmu overflow" state is checked in kvm_arch_vcpu_runnable(). > Fix this by checking the IRQ_PENDING VCPU request in runnable(). > Checking the request also sufficiently covers all the cases that > kvm_vgic_vcpu_pending_irq() cover, so we can just replace that. > > Signed-off-by: Andrew Jones > --- > virt/kvm/arm/arm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c > index 5bc9b0d2fd0f..725527f491e4 100644 > --- a/virt/kvm/arm/arm.c > +++ b/virt/kvm/arm/arm.c > @@ -423,7 +423,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu) > return !vcpu_should_sleep(vcpu) && > (vcpu->arch.mp_state != KVM_MP_STATE_HALTED || > (!!vcpu->arch.irq_lines || > - kvm_vgic_vcpu_pending_irq(vcpu))); > + kvm_test_request(KVM_REQ_IRQ_PENDING, vcpu))); So what if a VCPU blocks, a device raises an IRQ, the VCPU loops around, clears the KVM_REQ_IRQ_PENDING flag, enters the VM again, which does another WFI (for fun), and you end up here again with a pending IRQ but no KVM_REQ_IRQ_PENDING flag anymore. Doesn't this end up incorrectly stalling the VCPU? I don't think that a transient flag will work for a persistent binary state here. > } > > bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu) > -- > 2.13.5 > Thanks, -Christoffer