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

[Julien Grall <julien.grall@xxxxxxxxxx>]

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)
> 
> (credit to Jan for pointing this out in his review of Mukesh's x86
> variant)

The code was copied from relinquish_shared_pages
(arch/x86/mem_sharing.c), so if I'm not mistaken this code is also buggy.

-- 
Julien Grall

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