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Date: Mon, 21 May 2012 19:02:12 +0100
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>,
        "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] xen: do not map the same GSI twice
In-Reply-To: <20120521175142.GA13990@phenom.dumpdata.com>
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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).