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Re: [Xen-devel] [PATCH, resend] replacement for noirqdebug hack

On 2 Jun 2006, at 11:02, Jan Beulich wrote:

Instead of re-establishing the noirqdebug hack earlier present in the i386 Linux code, communicate the information about whether a particular IRQ is shared across domains from hypervisor to kernel.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

This is gross for a few reasons. Firstly it adds Xen cruft to a file we don't currently modify, and the changes would never be mergable upstream. Plus I'd prefer a lighter weight solution for handling this x86 crufty corner case -- adding extra bitmaps to shared_info and updating bits on every IRQ delivery is overkill imo.

What I would suggest is change note_interrupt() to only increment irqs_unhandled if some new function spurious_irqs_ok(irq) returns false. We can then define that function as Xen-specific and extend physdev_irq_status_query to be able to determine if an irq is shared across guests. We can avoid frequent hypercalls by caching the shared status the first time it evaluates true (so sharedness is sticky; I'd assume we would rarely take the path that executes the hypercall if the irq is really not shared).

 -- Keir

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