linux-kernel - Re: [PATCH RFC] kvm: enable irq injection from interrupt context

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Message-ID: <20100919112124.GD7350@redhat.com>
Date:	Sun, 19 Sep 2010 13:21:24 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] kvm: enable irq injection from interrupt context

On Sun, Sep 19, 2010 at 01:18:44PM +0200, Gleb Natapov wrote:
> On Sun, Sep 19, 2010 at 12:55:12PM +0200, Michael S. Tsirkin wrote:
> > On Sun, Sep 19, 2010 at 12:56:12PM +0200, Avi Kivity wrote:
> > >  On 09/19/2010 12:45 PM, Michael S. Tsirkin wrote:
> > > >On Fri, Sep 17, 2010 at 09:59:29AM +0200, Gleb Natapov wrote:
> > > >>  >  writing 0 to eventfd does nothing. The way to deassert irq
> > > >>  That is implementation detail of current irqfd. It was designed for MSI
> > > >>  not level triggered interrupts.
> > > >
> > > >Maybe we should add a check that gsi is mapped to MSI (or unmapped) then?
> > > >Level which switches to 1 and back to 0 immediately will be racy anyway
> > > >...
> > > >
> > > 
> > > Add a check where?
> > 
> > I would make sure that if you bind irqfd to a non-MSI GSI,
> > signalling it has no effect.
> > 
> Why would you do that? I am not against checking per se, but why a user of
> the API can't check for that?
> 
> --
> 			Gleb.

Currently using irqfd with level will kind of work, sometimes.
Better have it consistently not working so application
writers get the message that they can't rely on it.

-- 
MST
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