Re: [PATCH v4 06/10] memory: batch processing in acquire_resource()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 03.07.2020 13:36, Julien Grall wrote:
> On 03/07/2020 12:22, Jan Beulich wrote:
>> On 03.07.2020 13:17, Julien Grall wrote:
>>> In the current implementation, we tell the guest how many frames it can
>>> request in a batch. This number may be much smaller that the maximum
>>> number of frames of the type.
>>>
>>> Furthermore this value is not tie to the xmar.type. Therefore, it is
>>> valid for a guest to call this hypercall only once at boot to figure out
>>> the maximum batch.
>>>
>>> So while the change you suggest looks a good idea, I don't think it is
>>> possible to do that with the current hypercall.
>>
>> Doesn't the limit simply change to UINT_MAX >> MEMOP_EXTENT_SHIFT,
>> which then is what should be reported?
> 
> Hmmm... Can you remind me whether we support migration to an older release?

I'm pretty sure we say "N -> N+1 only" somewhere, but this "somewhere"
clearly isn't SUPPORT.md.

Jan