From mboxrd@z Thu Jan 1 00:00:00 1970 From: marc.zyngier@arm.com (Marc Zyngier) Date: Fri, 14 Mar 2014 14:40:22 +0000 Subject: [PATCH] KVM: ARM: vgic: plug irq injection race In-Reply-To: <20140314042052.GH24808@cbox> (Christoffer Dall's message of "Fri, 14 Mar 2014 04:20:52 +0000") References: <1392388086-24730-1-git-send-email-marc.zyngier@arm.com> <20140314042052.GH24808@cbox> Message-ID: <86d2horgh5.fsf@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Mar 14 2014 at 04:20:52 AM, Christoffer Dall wrote: > On Fri, Feb 14, 2014 at 02:28:06PM +0000, Marc Zyngier wrote: >> As it stands, nothing prevents userspace from injecting an interrupt >> before the guest's GIC is actually initialized. >> >> This goes unnoticed so far (as everything is pretty much statically >> allocated), but ends up exploding in a spectacular way once we switch >> to a more dynamic allocation (the GIC data structure isn't there yet). >> >> The fix is to test for the "ready" flag in the VGIC distributor before >> trying to inject the interrupt. Note that in order to avoid breaking >> userspace, we have to ignore what is essentially an error. >> >> Signed-off-by: Marc Zyngier >> --- >> virt/kvm/arm/vgic.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c >> index be456ce..d40fe61 100644 >> --- a/virt/kvm/arm/vgic.c >> +++ b/virt/kvm/arm/vgic.c >> @@ -1386,7 +1386,8 @@ out: >> int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num, >> bool level) >> { >> - if (vgic_update_irq_state(kvm, cpuid, irq_num, level)) >> + if (likely(vgic_initialized(kvm)) && > > Do we need a barrier in kvm_vgic_init before setting the > kvm->arch.vgic.ready to ensure we observe the correctly initialized > values of the irq_spi_cpu field here? Ah, I see. Yes, possibly. >> + vgic_update_irq_state(kvm, cpuid, irq_num, level)) >> vgic_kick_vcpus(kvm); >> >> return 0; >> -- >> 1.8.3.4 >> > > Otherwise looks good, nicely spotted! I'll respin something early next week. Cheers, M. -- Jazz is not dead. It just smells funny.