diff mbox

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

Message ID 000001d081cf$dd148fb0$973daf10$@astim.si (mailing list archive)
State New, archived
Headers show

Commit Message

Saso Slavicic April 28, 2015, 4:24 p.m. UTC 
> From: Paolo Bonzini
> Sent: Tuesday, April 21, 2015 10:48 AM


Hi, big thanks to all involved in this and to Brad for endless reboots ;-)


>> Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
>> Fixes: 33e4c68656a2e461b296ce714ec322978de85412
>> Cc: stable@vger.kernel.org # 2.6.32+
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>> 	The race was reported in 3.17+ by Brad Campbell and in
>> 	2.6.32 by Saso Slavicic, so it qualifies for stable.

> Patch for kernels before 3.17:

This will probably end up in RHEL6 sooner or later (but probably not before
6.7)?
As I like to experiment a bit, would this patch do for -2.6.32-504.12.2.el6
kernel? The code in that function is somewhat different...

 static inline int apic_search_irr(struct kvm_lapic *apic)


Regards,
Saso Slavicic

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Comments

Paolo Bonzini April 29, 2015, 4:45 p.m. UTC | #1 
On 28/04/2015 18:24, Saso Slavicic wrote:
> This will probably end up in RHEL6 sooner or later (but probably not before
> 6.7)?
> As I like to experiment a bit, would this patch do for -2.6.32-504.12.2.el6
> kernel? The code in that function is somewhat different...
> 
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -230,8 +230,13 @@
>  
>  static inline int apic_test_and_set_irr(int vec, struct kvm_lapic *apic)
>  {
> +	int ret = apic_test_and_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;
> -	return apic_test_and_set_vector(vec, apic->regs + APIC_IRR);
> +	return ret;
>  }
>  
>  static inline int apic_search_irr(struct kvm_lapic *apic)
> 
> 
> Regards,

Yes, this exact same patch is brewing in the RHEL6.7 internal trees...

See https://bugzilla.redhat.com/show_bug.cgi?id=1213741

Paolo
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diff mbox

Patch

--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -230,8 +230,13 @@ 
 
 static inline int apic_test_and_set_irr(int vec, struct kvm_lapic *apic)
 {
+	int ret = apic_test_and_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;
-	return apic_test_and_set_vector(vec, apic->regs + APIC_IRR);
+	return ret;
 }