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Re: [Xen-devel] xen: Clear IRQ_GUEST bit from irq_desc status if its act

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] xen: Clear IRQ_GUEST bit from irq_desc status if its action is NULL
From: Igor Mammedov <imammedo@xxxxxxxxxx>
Date: Tue, 13 Sep 2011 14:36:35 +0200
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On 09/13/2011 01:45 PM, Jan Beulich wrote:
On 13.09.11 at 11:08, Igor Mammedov<imammedo@xxxxxxxxxx>  wrote:
On a system with Intel C600 series Patsburg SAS controller
if following command are executed:

   rmmod isci
   modprobe isci

the host will crash in pirq_guest_bind in attempt to dereference
NULL action pointer.

This is caused by isci driver which does not cleanup irq properly,
removing device first and then os tries to unbind its irqs afterwards.

c/s 20093 and 20844 fixed host crashes when removing isci module.

However in dynamic_irq_cleanup 'action' field of irq_desc is set to
NULL but IRQ_GUEST flag in 'status' field is not cleared. So on next

So why don't you clear the bit there?

then we may hit

BUG_ON(!(desc->status & IRQ_GUEST));

in pirq_guest_unbind -> __pirq_guest_unbind

It seams safer for me to clear bit in __pirq_guest_unbind

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