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

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Date:	Tue, 27 Apr 2010 12:58:16 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Prarit Bhargava <prarit@...hat.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 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?
> 
> 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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