Re: [PATCH v6 07/12] xen: enable Dom0 to use SVE feature

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

> On 24 Apr 2023, at 17:10, Jan Beulich <jbeulich@xxxxxxxx> wrote:
> 
> On 24.04.2023 17:43, Luca Fancellu wrote:
>>> On 24 Apr 2023, at 16:41, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>> On 24.04.2023 17:34, Luca Fancellu wrote:
>>>>> On 24 Apr 2023, at 16:25, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>>> On 24.04.2023 17:18, Luca Fancellu wrote:
>>>>>> Oh ok, I don’t know, here what I get if for example I build arm32:
>>>>>> 
>>>>>> arm-linux-gnueabihf-ld -EL -T arch/arm/xen.lds -N prelink.o \
>>>>>> ./common/symbols-dummy.o -o ./.xen-syms.0
>>>>>> arm-linux-gnueabihf-ld: prelink.o: in function `create_domUs':
>>>>>> (.init.text+0x13464): undefined reference to `sve_domctl_vl_param'
>>>>> 
>>>>> In particular with seeing this: What you copied here is a build with the
>>>>> series applied only up to this patch? I ask because the patch here adds a
>>>>> call only out of create_dom0().
>>>> 
>>>> No I’ve do the changes on top of the serie, I’ve tried it now, only to 
>>>> this patch and it builds correctly,
>>>> It was my mistake to don’t read carefully the error output.
>>>> 
>>>> Anyway I guess this change is not applicable because we don’t have a 
>>>> symbol that is plain 0 for domUs
>>>> to be placed inside create_domUs.
>>> 
>>> Possible, but would you mind first telling me in which other patch(es) the
>>> further reference(s) are being introduced, so I could take a look without
>>> (again) digging through the entire series?
>> 
>> Sure, the other references to the function are introduced in "xen/arm: add 
>> sve property for dom0less domUs” patch 11
> 
> Personally I'm inclined to suggest adding "#ifdef CONFIG_ARM64_SVE" there.
> But I guess that may again go against your desire to not ignore inapplicable
> options. Still I can't resist to at least ask how an "sve" node on Arm32 is
> different from an entirely unknown one.

It would be ok for me to use #ifdef CONFIG_ARM64_SVE and fail in the #else 
branch,
but I had the feeling in the past that Arm maintainers are not very happy with 
#ifdefs, I might
be wrong so I’ll wait for them to give an opinion and then I will be happy to 
follow.

> 
> Jan