Re: [Xen-devel] [PATCH v5 08/10] xen/arm: Add relinquish_p2m_mapping to remove reference on every mapped page

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-12-17 at 14:40 +0000, Julien Grall wrote:
> On 12/17/2013 09:26 AM, Ian Campbell wrote:
> > On Mon, 2013-12-16 at 17:37 +0000, Julien Grall wrote:
> >> +        if ( op == RELINQUISH && count == LPAE_ENTRIES &&
> >> +             hypercall_preempt_check() )
> >> +        {
> > 
> > If hypercall_preempt_check returns false the first time it is called
> > then you won't ever try again. I think you want
> >     (count+1 % LPAE_ENTRIES) == 0
> > (the +1 avoids preempting without having done any work yet)
> 
> I don't think we need +1 because count is increment each round just
> before the check.

Ah yes, if the increment has already happened then good.

> Is a solution as Jan made for x86 would be more appropriate?

It's about equivalent I think? I'd hope the compiler would take a mod
2^N and turn it into a mask, but I suppose you never know...

Ian.


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