Re: [Xen-devel] [PATCH v3 08/24] xen/arm: Allow virq != irq

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-02-27 at 14:33 +0000, Julien Grall wrote:
> Hi Ian,
> 
> On 20/02/15 17:09, Julien Grall wrote:
> > On 20/02/15 15:52, Ian Campbell wrote:
> >>>  
> >>>      action = xmalloc(struct irqaction);
> >>> -    if (!action)
> >>> +    if ( !action )
> >>> +        return -ENOMEM;
> >>> +
> >>> +    info = xmalloc(struct irq_guest);
> >>
> >> FWIW you might (subject to sizing/alignment needs) be able to do
> >>    action = _xmalloc(sizeof(struct irqaction) + sizeof(struct irq_guest);
> >>    info = (sturct irq_guest *)(action + 1);
> >>
> >> which would save some memory overhead for free pointers etc and allow
> >> you to avoid manually managing the info.
> >>
> >> You probably won't like that though, so feel free to ignore.
> > 
> > Actually it's a good idea :). I haven't though about it.
> 
> I though about it. The pointer to irq_guest may not be correctly aligned
> with this solution, right?

It depends on sizeof(struct irqaction) (which is what I meant by
"subject to..."). t'd probably need a ROUNDUP(sizeof(foo),
pointer-alignement) in there somewhere.

> So I prefer to keep separate the allocation. We can revisit it later.

OK.




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