linux-kernel - Re: [LKML] [PATCH] Fix NULL pointer for Xen guests

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Date:	Tue, 27 Apr 2010 13:09:01 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	linux-kernel@...r.kernel.org, suresh.b.siddha@...el.com,
	x86@...nel.org, clalance@...hat.com, drjones@...hat.com
Subject: Re: [LKML] [PATCH] Fix NULL pointer for Xen guests



On 04/27/2010 12:58 PM, Konrad Rzeszutek Wilk wrote:
> On Tue, Apr 27, 2010 at 11:24:42AM -0400, Prarit Bhargava wrote:
>    
>> Upstream PV guests fail to boot because of a NULL pointer.  It is possible that
>> xen guests have irq_desc->chip_data = NULL.
>>      
> Can you provide a short example of test scenario? As in what I should do
> to reproduce this problem?
>    

Take the latest upstream (well ... to be honest, a bit older than that 
because of some other bugs) -- take 2.6.33 and try to boot it as a PV 
guest.  I'm using a RHEL5 Xen HV fwiw ...

P.

>> Test for NULL chip_data pointer before attempting to complete an irq move.
>>
>> Signed-off-by: Prarit Bhargava<prarit@...hat.com>
>> Acked-by: Suresh Siddha<suresh.b.siddha@...el.com>
>>
>> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
>> index 127b871..eb2789c 100644
>> --- a/arch/x86/kernel/apic/io_apic.c
>> +++ b/arch/x86/kernel/apic/io_apic.c
>> @@ -2545,6 +2545,9 @@ void irq_force_complete_move(int irq)
>>   	struct irq_desc *desc = irq_to_desc(irq);
>>   	struct irq_cfg *cfg = desc->chip_data;
>>
>> +	if (!cfg)
>> +		return;
>> +
>>   	__irq_complete_move(&desc, cfg->vector);
>>   }
>>   #else
>> --
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