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Re: [Xen-devel] problem in setting cpumask for physical interrupt

To: "Agarwal, Lomesh" <lomesh.agarwal@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] problem in setting cpumask for physical interrupt
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 26 Oct 2007 07:42:03 +0100
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An event channel can only be bound to one VCPU at a time. The IRQ should be bound to the CPU that that VCPU runs on.

 -- Keir

On 26/10/07 01:36, "Agarwal, Lomesh" <lomesh.agarwal@xxxxxxxxx> wrote:

Why does function pirq_guest_bind (in arch/x86/irq.c) calls set_affinity with cpumask of current processor? If I understand correctly pirq_guest_bind is called in response to guest calling request_irq. So, if by chance all guests call request_irq on the same physical processor then Xen may end up setting interrupt affinity to one physical processor only.
I think Xen should set the affinity to all the processors available. VCPU is not guranteed to run on the same physical processor on which it called request_irq anyway.
I will send a patch if my understanding looks ok.


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