[PATCH] powerpc: Add support for VRSAVE

[Sebastian Huber]

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.

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