Re: [Xen-devel] [PATCH 1/2] xen/x86: return partial memory map in case of not enough space

[Juergen Gross <jgross@xxxxxxxx>]

On 06/12/16 09:51, Jan Beulich wrote:
>>>> On 06.12.16 at 09:33, <JGross@xxxxxxxx> wrote:
>> On 06/12/16 09:15, Jan Beulich wrote:
>>> I'd like us to at least consider alternatives:
>>>
>>> 1) Have a new sub-op behaving BIOS like (one entry at a time).
>>
>> No objections from me.
>>
>>> 2) Make the full map available inside the initial mapping, pointed to
>>> by a new entry in the start info structure.
>>
>> What about PVH?
> 
> Does PVH re-arrangement of its physical memory too? I didn't think
> so ...

Not yet. Are you sure it won't be needed in future? Why was it done in
the pvops kernel? I thought the main reason was to have the same PCI
space address layout as on the native system in order to avoid any bad
surprises due to buggy firmware and/or BIOS. The same could apply for
PVH.

>>> 3) Have pvops Linux make use of the extra space available at the
>>> end of the initial mapping. The minimum of 512k there should be
>>> more than enough.
>>
>> This would mean using this area as a temporary buffer and copying the
>> obtained map somewhere else (either only in the size of the static
>> buffer or after reorganizing the memory according to the map). I guess
>> this would work, too.
>>
>>> 4) Others I can't think of right now.
>>
>> My preference would be 1). In case we are choosing this approach I
>> don't see any need for the other patch I sent for getting the number
>> of entries. It can easily be replaced by a loop of the single entry
>> solution.
> 
> Well, my preference would be 3), then 2), then 1).

If nobody is objecting I can go that route (3).

> Regardless of that I would welcome patch 2 to be re-submitted
> without depending on patch 1, as I think this is a worthwhile
> adjustment in any case (bringing the interface in line with what
> we do elsewhere).

Sure, will do.


Juergen

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