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Re: [Xen-devel] Interrupt forwarding

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Interrupt forwarding
From: Jon Smirl <jonsmirl@xxxxxxxxx>
Date: Sat, 12 Mar 2005 13:33:25 -0500
Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, ian.pratt@xxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxxx
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Reply-to: Jon Smirl <jonsmirl@xxxxxxxxx>
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On Sat, 12 Mar 2005 18:21:19 +0000, Keir Fraser
<Keir.Fraser@xxxxxxxxxxxx> wrote:
> On 12 Mar 2005, at 18:11, Ian Pratt wrote:
> > Shared interrupts aren't good news for performance, but they work OK.
> >
> > If a driver domain locks up we can kill and restart it -- for safety we
> > don't rely on it to ack the interrupt.
> Shared interrupts are slightly worse because the irq won't get unmasked
> until all receivers say their work is done. If one lock sup it starves
> the rest -- until this is detected and that domain gets blown away.

After you blow away the domain how do you acknowledge the interrupt?
Is all hardware required to have a tiny driver in the supervisor to
handling acking in this case? If you don't ack it, it is going to keep

> Fortunately the days of shared interrupts are numbered with MSI and
> PCI-Express.
>   -- Keir

Jon Smirl

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