Re: [PATCH stable] KVM: x86: Fix lost interrupt on irr_pending race

Paolo Bonzini
2015-04-22T13:47:13Z

On 22/04/2015 15:34, Luis Henriques wrote:
> Thanks Paolo. I was going to apply this backport to the 3.16 kernel
> but it looks like the original commit is a clean cherry-pick. Shall I
> still apply your backport, or do you think the original commit should
> be applied instead?

Indeed you're right. I wrote the backport for 3.16(.0). However,
commit 56cc2406d68c0f09505c389e276f27a99f495cbd was marked for stable,
so it's necessary to cherry-pick the entire patch on the stable kernel
where the buggy commit was backported.

That should be, according to the stable@vger.kernel.org archives,
3.10.54+, 3.13.11.7+, 3.14.18+, 3.16.2+.

Paolo

> Cheers,
> --
> Luís
>
>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
>> index 6e8ce5a1a05d..e0e5642dae41 100644
>> --- a/arch/x86/kvm/lapic.c
>> +++ b/arch/x86/kvm/lapic.c
>> @@ -341,8 +341,12 @@ EXPORT_SYMBOL_GPL(kvm_apic_update_irr);
>>
>> static inline void apic_set_irr(int vec, struct kvm_lapic *apic)
>> {
>> - apic->irr_pending = true;
>> apic_set_vector(vec, apic->regs + APIC_IRR);
>> + /*
>> + * irr_pending must be true if any interrupt is pending; set it after
>> + * APIC_IRR to avoid race with apic_clear_irr
>> + */
>> + apic->irr_pending = true;
>> }
>>
>> static inline int apic_search_irr(struct kvm_lapic *apic)
>>
>>
>> Thanks,
>>
>> Paolo
>> --
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