linux-kernel - Re: [PATCH v4 0/4] selftests: Fix cpuid / vendor checking build issues

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Message-ID: <b4b7147f-64cf-4244-a896-07a88f08d0f1@linuxfoundation.org>
Date: Wed, 4 Sep 2024 06:30:08 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc: Shuah Khan <shuah@...nel.org>, Reinette Chatre
 <reinette.chatre@...el.com>, linux-kselftest@...r.kernel.org,
 LKML <linux-kernel@...r.kernel.org>,
 Shaopeng Tan <tan.shaopeng@...fujitsu.com>, Fenghua Yu
 <fenghua.yu@...el.com>,
 Maciej Wieczór-Retman <maciej.wieczor-retman@...el.com>,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v4 0/4] selftests: Fix cpuid / vendor checking build
 issues

On 9/4/24 06:18, Ilpo Järvinen wrote:
> On Tue, 3 Sep 2024, Shuah Khan wrote:
> 
>> On 9/3/24 08:45, Ilpo Järvinen wrote:
>>> This series first generalizes resctrl selftest non-contiguous CAT check
>>> to not assume non-AMD vendor implies Intel. Second, it improves
>>> selftests such that the use of __cpuid_count() does not lead into a
>>> build failure (happens at least on ARM).
>>>
>>> While ARM does not currently support resctrl features, there's an
>>> ongoing work to enable resctrl support also for it on the kernel side.
>>> In any case, a common header such as kselftest.h should have a proper
>>> fallback in place for what it provides, thus it seems justified to fix
>>> this common level problem on the common level rather than e.g.
>>> disabling build for resctrl selftest for archs lacking resctrl support.
>>>
>>> I've dropped reviewed and tested by tags from the last patch in v3 due
>>> to major changes into the makefile logic. So it would be helpful if
>>> Muhammad could retest with this version.
>>>
>>> Acquiring ARCH in lib.mk will likely allow some cleanup into some
>>> subdirectory makefiles but that is left as future work because this
>>> series focuses in fixing cpuid/build.
>>
>>>
>>> v4:
>>> - New patch to reorder x86 selftest makefile to avoid clobbering CFLAGS
>>>     (would cause __cpuid_count() related build fail otherwise)
>>>
>> I don't like the way this patch series is mushrooming. I am not
>> convinced that changes to lib.mk and x86 Makefile are necessary.
> 
> I didn't like it either what I found from the various makefiles. I think
> there are many things done which conflict with what lib.mk seems to try to
> do.
> 

Some of it by desig. lib.mk offers framework for common things. There
are provisions to override like in the case of x86, powerpc. lib.mk
tries to be flexible as well.

> I tried to ask in the first submission what test I should use in the
> header file as I'm not very familiar with how arch specific is done in
> userspace in the first place nor how it should be done within kselftest
> framework.
> 

Thoughts on cpuid:

- It is x86 specific. Moving this to kselftest.h was done to avoid
   duplicate. However now we are running into arm64/arm compile
   errors due to this which need addressing one way or the other.

I have some ideas on how to solve this - but I need answers to
the following questions.

This is a question for you and Usama.

- Does resctrl run on arm64/arm and what's the output?
- Can all other tests in resctrl other tests except
   noncont_cat_run_test?
- If so send me the output.

thanks,
-- Shuah