linux-kernel - Re: [PATCH 0/2] kvm: fix spurious interrupt with irqfd

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Message-ID: <20100120145822.GB3434@redhat.com>
Date:	Wed, 20 Jan 2010 16:58:22 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	mtosatti@...hat.com, Davide Libenzi <davidel@...ilserver.org>,
	kvm@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] kvm: fix spurious interrupt with irqfd

On Wed, Jan 20, 2010 at 04:10:37PM +0200, Avi Kivity wrote:
> On 01/19/2010 04:52 PM, Michael S. Tsirkin wrote:
>> On Sun, Jan 17, 2010 at 02:42:50PM +0200, Avi Kivity wrote:
>>    
>>> On 01/13/2010 07:12 PM, Michael S. Tsirkin wrote:
>>>      
>>>> Deassigning irqfd and assigning back caused spurious interrupt. fix this
>>>> by clearing the counter on deassign.  This is on top of davidel's patch
>>>> which makes clearing eventfd counter from modules possible.
>>>>
>>>>        
>>> Applied both, thanks.
>>>      
>> Hmm, I see this in kvm master.  Avi/Marcelo, since this is a bugfix, can
>> you queue this patchset for 2.6.33 and 2.6.32 stable as well please?
>>    
>
> I'm uncomfortable with pushing Davide's patch into stable and possibly  
> causing regressions with unrelated applications.  Can't a guest live  
> with a spurious interrupt?

Well guests mask/unmask vector on each interrupt, so this will trigger
an irq storm I think.

>  It's not like they're unknown.

Depends on the device really.
In theory, if they trigger at an unfortunate time this could cause
crashes.



-- 
MST
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