From: marc.zyngier@arm•com (Marc Zyngier)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] KVM: ARM: vgic: plug irq injection race
Date: Fri, 14 Mar 2014 14:40:22 +0000 [thread overview]
Message-ID: <86d2horgh5.fsf@arm.com> (raw)
In-Reply-To: <20140314042052.GH24808@cbox> (Christoffer Dall's message of "Fri, 14 Mar 2014 04:20:52 +0000")
On Fri, Mar 14 2014 at 04:20:52 AM, Christoffer Dall <christoffer.dall@linaro•org> 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 <marc.zyngier@arm•com>
>> ---
>> 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.
next prev parent reply other threads:[~2014-03-14 14:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-14 14:28 [PATCH] KVM: ARM: vgic: plug irq injection race Marc Zyngier
2014-03-14 4:20 ` Christoffer Dall
2014-03-14 14:40 ` Marc Zyngier [this message]
2014-03-14 19:09 ` Christoffer Dall
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