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

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Date:	Mon, 18 Oct 2010 23:17:53 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Yinghai Lu <yinghai@...nel.org>
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 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.

Thanks,

	tglx
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