Re: [Xen-devel] [PATCH v4 3/5] xen/arm: vgic: Optimize the way to store the target vCPU in the rank

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2015-10-22 at 18:15 +0100, Julien Grall wrote:
> Hi Ian,
> 
> On 22/10/15 17:17, Ian Campbell wrote:
> > On Mon, 2015-10-12 at 15:22 +0100, Julien Grall wrote:
> > > [...]
> > >          /* Only migrate the vIRQ if the target vCPU has changed */
> > >          if ( new_target != old_target )
> > >          {
> > > +            unsigned int virq = rank->index * NR_INTERRUPT_PER_RANK
> > > + offset;
> > 
> > FWIW this was the value of offset before it was shifted + masked, I
> > think.
> > Could you not just save it up top and remember it?
> 
> In fact, the virq is already correctly set before the loop (see patch
> #2):
> 
> virq = rank->index * NR_INTERRUPT_PER_RANK + offset;
> 
> The variable is incremented in the for loop. So I just forgot to drop
> this line when I did the split.
> 
> Not that it's not possible to use directly offset because for byte
> access it will point to the byte modified and not the base address of
> the register.
> 
> Though, I could use a mask, but I find this solution clearer.

But per the above what is actually going to happen is you drop this change?

Ian.

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