linux-kernel - Re: [PATCH 11/14] xen: events: dynamically allocate irq info structures

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Message-ID: <1299747091.17339.728.camel@zakaz.uk.xensource.com>
Date:	Thu, 10 Mar 2011 08:51:31 +0000
From:	Ian Campbell <Ian.Campbell@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
Subject: Re: [PATCH 11/14] xen: events: dynamically allocate irq info
 structures

On Thu, 2011-03-10 at 05:27 +0000, Konrad Rzeszutek Wilk wrote:
> > @@ -649,10 +653,9 @@ int xen_bind_pirq_gsi_to_irq(unsigned gsi,
> >  
> >  	spin_lock(&irq_mapping_update_lock);
> >  
> > -	if ((pirq > nr_irqs) || (gsi > nr_irqs)) {
> > -		printk(KERN_WARNING "xen_map_pirq_gsi: %s %s is incorrect!\n",
> > -			pirq > nr_irqs ? "pirq" :"",
> > -			gsi > nr_irqs ? "gsi" : "");
> > +	if (pirq > nr_irqs) {
> > +		printk(KERN_WARNING "xen_map_pirq_gsi: pirq %d > nr_irqs %d!\n",
> > +		       pirq, nr_irqs);
> 
> Looks like this belongs to another patch?

To be honest I'm not entirely sure what that check was protecting
anyway. Possibly it comes from a time when the GSI<->IRQ was 1-1 and
prevented us from spilling off the end of the irq_info array.

It may be that it is safe to have gsi > nr_irqs in an earlier patch in
this series (possibly "xen: events: maintain a list of Xen interrupts")
or even in one of my earlier series which switched to using the core
interrupt allocation logic and/or removed the 1-1 mapping above
nr_irqs_gsi in certain cases.

Anyway, this is the first patch where I'm pretty sure it is safe to
allow GSI > nr_irqs since there are no nr_irqs based limitations left
apart from the pirq one.

Ian.

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