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

[Julien Grall <julien.grall@linaro.org>]

On 12/17/2013 02:42 PM, Ian Campbell wrote:
> 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...

I was talking about adding a greater increment when it's a foreign mapping.

-- 
Julien Grall