Re: [Xen-devel] [PATCH] memory: don't suppress P2M update in populate_physmap()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.06.17 at 14:51, <julien.grall@xxxxxxx> wrote:
> On 06/20/2017 01:40 PM, Andrew Cooper wrote:
>> On 20/06/17 13:39, Julien Grall wrote:
>>> On 06/20/2017 09:37 AM, Andrew Cooper wrote:
>>>> On 20/06/17 07:19, Jan Beulich wrote:
>>>>> Commit d18627583d ("memory: don't hand MFN info to translated guests")
>>>>> wrongly added a null-handle check there - just like stated in its
>>>>> description for memory_exchange(), the array is also an input for
>>>>> populate_physmap() (and hence can't reasonably be null). I have no idea
>>>>> how I've managed to overlook this.
>>>>>
>>>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>>
>>>> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>>
>>> Am I correct that this is not a bug and only a pointless check?
>> 
>> This is a partial reversion of d18627583d and needs to be included in
>> 4.9, to avoid a regression.
> 
> Would you mind to explain why this would introduce regression? AFAICT 
> the check is just redundant, so keeping it is not that bad.

Afaict there would be a regression only if someone invoked the
hypercall with a null handle (but having valid data at address zero).
Still I agree with Andrew that we'd better include this in 4.9.

Jan


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