Re: xen: Clear IRQ_GUEST bit from irq_desc status if its action is NULL

[Igor Mammedov <imammedo@redhat.com>]

On 09/13/2011 01:45 PM, Jan Beulich wrote:
>>>> On 13.09.11 at 11:08, Igor Mammedov<imammedo@redhat.com>  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