Re: Some questions about using the perf tool in ARM-SPE

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 17/07/2023 06:57, Leo Yan wrote:
> Hi Suzuki,
> 
> On Wed, Jul 05, 2023 at 10:33:18AM -0700, Namhyung Kim wrote:
>> On Mon, Jul 3, 2023 at 6:33 AM Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
>>> On 03/07/2023 11:20, Leo Yan wrote:
>>>> On Mon, Jul 03, 2023 at 10:42:21AM +0100, James Clark wrote:
> 
> [...]
> 
>>> Do we somehow sync (copy) the cputype.h for perf tool ? Or do we keep
>>> them in sync with a patch ?
>>>
>>> If it is the former, I wouldn't bother about updating the kernel
>>> headers.
>>
>> In general, perf tool has a copy of kernel headers and there's a script
>> called check-headers.sh to verify they are in sync.  We don't
>> recommend kernel patches to touch the tool's copy.  And it's done
>> by tool devs separately.
> 
> We have the kernel header arch/arm64/include/asm/cputype.h, tools have a
> copy which is placed in tools/arch/arm64/include/asm/cputype.h.
> 
> As Namhyung explained, usually the kernel header is firstly changed and
> then the tool developers send a separate patch to sync with kernel
> header.  You could see a recent example by Arnaldo's patch [1].
> 
> By following this working model, I sent patch series to add Cortex-X4
> CPU part and MIDR definitions.  I personally think this is the best
> way for us to keep the alignment between the kernel header and tools
> header [2].  Please let me know if this doable or not?
Sure, if the tool relies on syncing the kernel headers, thats fine.

> 
> Sorry for late response due to vacation :)

No worries, I will dig the series from the mailing list and
respond there. Thanks for sending this out.

Suzuki

> 
> Thanks,
> Leo
> 
> [1] https://lore.kernel.org/lkml/ZLFQ%2Ftu%2FATQwDEIW@kernel.org/
> [2] https://lore.kernel.org/lkml/20230717054327.79815-1-leo.yan@linaro.org/