[PATCH] powerpc: Add support for VRSAVE

[Chris Johns]

On 5/9/2022 4:36 pm, Sebastian Huber wrote:
> On 03/09/2022 01:17, Chris Johns wrote:
>> On 2/9/2022 2:27 pm, Sebastian Huber wrote:
>>> On 02.09.22 06:22, Sebastian Huber wrote:
>>>> On 02.09.22 04:22, Chris Johns wrote:
>>>>> On 1/9/2022 6:26 pm, Sebastian Huber wrote:
>>>>>> The VRSAVE feature of the Altivec unit can be used to reduce the amount of
>>>>>> Altivec registers which need to be saved/restored during interrupt processing
>>>>>> and context switches.
>>>>> Which BSPs and hardware has this been tested on?
>>>> The e6500 QoIQ BSPs.
>>> I mean QorIQ. We have this code since 2020 in production code. I just forgot to
>>> integrate it.
>> I would like to have this tested on some of the older MVME boards. Do you still
>> have the mvme5500 (I think)? I can look at testing in an mvme2703 this week.
> 
> This will not work out of the box. In order to use the VRSAVE optimization, you
> need also a corresponding multilib (-mvrsave), see GCC patch. The MVME BSPs use
> a different exception and context switch code for the AltiVec support. You would
> have to convert them first to the implementation used by the QorIQ BSPs. Lastly,
> you also have add the -mvrsave flag to the ABI_FLAGS.

Thank you for the explanation. This was not apparent to me so maybe something in
the commit message to help anyone reviewing the change would help?

Which BSPs does this effect?

Chris