Re: [PATCH] selftests: resctrl: ignore builds for unsupported architectures

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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Adding Maciej.

On Fri, 9 Aug 2024, Muhammad Usama Anjum wrote:
> On 8/9/24 12:23 PM, Ilpo Järvinen wrote:
> > On Fri, 9 Aug 2024, Muhammad Usama Anjum wrote:
> > 
> >> This test doesn't have support for other architectures. Altough resctrl
> >> is supported on x86 and ARM, but arch_supports_noncont_cat() shows that
> >> only x86 for AMD and Intel are supported by the test.
> > 
> > One does not follow from the other. arch_supports_noncont_cat() is only 
> > small part of the tests so saying "This test" based on a small subset of 
> > all tests is bogus. Also, I don't see any reason why ARCH_ARM could not be 
> > added and arch_supports_noncont_cat() adapted accordingly.
> I'm not familiar with resctrl and the architectural part of it. Feel
> free to fix it and ignore this patch.
> 
> If more things are missing than just adjusting
> arch_supports_noncont_cat(), the test should be turned off until proper
> support is added to the test.
>
> >> We get build
> >> errors when built for ARM and ARM64.
> > 
> > As this seems the real reason, please quote any errors when you use them 
> > as justification so it can be reviewed if the reasoning is sound or not.
> 
>   CC       resctrl_tests
> In file included from resctrl.h:24,
>                  from cat_test.c:11:
> In function 'arch_supports_noncont_cat',
>     inlined from 'noncont_cat_run_test' at cat_test.c:323:6:
> ../kselftest.h:74:9: error: impossible constraint in 'asm'
>    74 |         __asm__ __volatile__ ("cpuid\n\t"
>        \
>       |         ^~~~~~~
> cat_test.c:301:17: note: in expansion of macro '__cpuid_count'
>   301 |                 __cpuid_count(0x10, 1, eax, ebx, ecx, edx);
>       |                 ^~~~~~~~~~~~~
> ../kselftest.h:74:9: error: impossible constraint in 'asm'
>    74 |         __asm__ __volatile__ ("cpuid\n\t"
>        \
>       |         ^~~~~~~
> cat_test.c:303:17: note: in expansion of macro '__cpuid_count'
>   303 |                 __cpuid_count(0x10, 2, eax, ebx, ecx, edx);
>       |                 ^~~~~~~~~~~~~

Okay, so it's specific to lack of CPUID. This seems a kselftest common 
level problem to me, since __cpuid_count() is provided in kselftest.h.

Shuah (or others), what is the intended mechanism for selftests to know if 
it can be used or not since as is, it's always defined?

I see some Makefiles use compile testing a trivial program to decide whether 
they build some x86_64 tests or not. Is that what should be done here too, 
test if __cpuid_count() compiles or not (and then build some #ifdeffery 
based on the result of that compile testing)?

-- 
 i.