linux-kernel - Re: [PATCH] xen: do not map the same GSI twice

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Date:	Mon, 21 May 2012 19:02:12 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xen: do not map the same GSI twice

On Mon, 21 May 2012, Konrad Rzeszutek Wilk wrote:
> On Mon, May 21, 2012 at 06:47:44PM +0100, Stefano Stabellini wrote:
> > On Mon, 21 May 2012, Konrad Rzeszutek Wilk wrote:
> > > On Mon, May 21, 2012 at 04:54:10PM +0100, Stefano Stabellini wrote:
> > > > PV on HVM guests map GSIs into event channels; at restore time the
> > > > event channels are resumed by restore_pirqs.
> > > > Device drivers might try to register the same GSI again through ACPI at
> > > > restore time, but the GSI has already been mapped and bound by
> > > > restore_pirqs.
> > > 
> > > Which means... what kind of error do we get without this patch?
> > 
> > Xen would print:
> > 
> > (XEN) irq.c:2235: dom4: pirq 23 or emuirq 28 already mapped
> > 
> > and waste a pirq
> 
> OK. This sounds like it has been a bug since ..oh forever then?
> 

Yes. It only showed up since the ata_piix driver started registering the
GSI again on resume (I don't know when this behavior started exactly).
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