Re: [Xen-devel] [PATCH v5 p2 01/19] xen/arm: Let the toolstack configure the number of SPIs

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 16/04/2015 15:39, Ian Campbell wrote:
> On Thu, 2015-04-09 at 16:09 +0100, Julien Grall wrote:
> > From: Julien Grall <julien.grall@xxxxxxxxxx>
> >
> > Each domain may have a different number of IRQs depending on the devices
> > assigned to it.
> > Rather re-using the number of IRQs used by the hardwared GIC, let the
>           ^than
>
> > toolstack specify the number of SPIs when the domain is created. This
> > will avoid to waste memory.
>    "will avoid wasting memory."
>
>
> > +    /* Limit the number of virtual SPIs supported to (1020 - 32) = 988  */
> > +    if ( (nr_spis + NR_LOCAL_IRQS) > 1020 )
> > +        return -EINVAL;
> If there's any chance this can be called by not-completely trusted code
> (e.g. a disaggregated toolstack) then this if susceptible to an overflow
> (sorry, I gave you this code in a previous rev).
Hmmm, right.


> I think you can just move the NR_LOCAL_IRQS to the other side of the
> expression, i.e.
>      if ( nr_spis > 1020 - NR_LOCAL_IRQS )
I will do the change and adding a pair of parentheses for more clarity:

if ( nr_spis > (1020 - NR_LOCAL_IRQS) )

> With that and the grammar fixed:
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Thanks,

--
Julien Grall

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