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

[Igor Mammedov <imammedo@xxxxxxxxxx>]

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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