linux-kernel - Re: [PATCH] x86, irq: Check if irq is remapped before freeing irte

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Message-Id: <54A1618A-3DAC-43A7-8FCD-1EE8992F7413@kernel.org>
Date:	Mon, 18 Oct 2010 14:28:18 -0700
From:	Yinghai <yinghai@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, irq: Check if irq is remapped before freeing irte



On Oct 18, 2010, at 2:17 PM, Thomas Gleixner <tglx@...utronix.de> wrote:

> 
> 
> On Mon, 18 Oct 2010, Thomas Gleixner wrote:
> 
>> On Mon, 18 Oct 2010, Yinghai Lu wrote:
>>> 
>>> Index: linux-2.6/drivers/pci/intr_remapping.c
>>> ===================================================================
>>> --- linux-2.6.orig/drivers/pci/intr_remapping.c
>>> +++ linux-2.6/drivers/pci/intr_remapping.c
>>> @@ -60,7 +60,7 @@ int get_irte(int irq, struct irte *entry
>>>    unsigned long flags;
>>>    int index;
>>> 
>>> -    if (!entry || !irq_iommu)
>>> +    if (!entry || !irq_iommu || !irq_iommu->iommu)
>>>        return -1;
>> 
>> Hmm, why do we need this? This is only called from
>> ir_ioapic_set_affinity() and ir_msi_set_affinity().
>> 
>> We should never end up there when intr_remapping=off, right ?
> 
> Thinking more about it, this check is actively bogus. The call sites do:
> 
>        struct irte irte;
> 
>        if (get_irte(irq, &irte))
>                return -1;
> 
> So entry _CANNOT_ be NULL.
> 
> And in fact we should change get_irte() to
> 
> get_irte(struct irq_2_iommu *irq_iommu, struct irte *entry)
> 
> The call site already knows about it. No need to lookup irq_iommu
> based on the irq number.

Yes
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