linux-kernel - Re: [KVM PATCH v5 0/4] irqfd fixes and enhancements

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Message-ID: <4A4772B5.5030008@redhat.com>
Date:	Sun, 28 Jun 2009 16:40:05 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Gregory Haskins <ghaskins@...ell.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, mst@...hat.com,
	paulmck@...ux.vnet.ibm.com, davidel@...ilserver.org,
	rusty@...tcorp.com.au
Subject: Re: [KVM PATCH v5 0/4] irqfd fixes and enhancements

On 06/28/2009 03:59 PM, Gregory Haskins wrote:
>> I agree that we want POLLHUP support, it's better than holding on to
>> the eventfd.  But I think we can make it even cleaner by merging it
>> with deassign.  Basically, when we get POLLHUP, we launch a slow_work
>> (or something) that does a regular deassign.  That slow_work can grab
>> a ref to the vm, so we don't race with the VM disappearing.
>>
>> But given that the current slow_work does almost nothing, I'm not sure
>> it's worth it.
>>      
>
> Yeah, and also note that the algorithm to unhook each side is not quite
> symmetrical.  I think I've captured all the common parts (in things like
> irqfd_deactivate(), etc).  A minor change in kvm_irqfd_release() could
> technically use a deferred job to release instead of doing it inline,
> but I do not think it buys us very much to do so (as you pointed out,
> the defered part is actually fairly simple).  The important parts of the
> protocol lie outside of the work we can do in the work-item anyway.
>    

Is the case of deassign vs POLLHUP covered?

Reusing deassign in POLLHUP at least makes it easy to verify that it is.

-- 
error compiling committee.c: too many arguments to function

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