Re: [PATCH] selftests:resctrl: Fix build failure on archs without __cpuid_count()

[Shuah Khan]

On 9/6/24 01:35, Muhammad Usama Anjum wrote:
> Hi Shuah,
>
> Thank you for fixing it.
>
> On 9/5/24 11:02 PM, Shuah Khan wrote:
> > When resctrl is built on architectures without __cpuid_count()
> > support, build fails. resctrl uses __cpuid_count() defined in
> > kselftest.h.
> >
> > Even though the problem is seen while building resctrl on aarch64,
> > this error can be seen on any platform that doesn't support CPUID.
> >
> > CPUID is a x86/x86-64 feature and code paths with CPUID asm commands
> > will fail to build on all other architectures.
> >
> > All others tests call __cpuid_count() do so from x86/x86_64 code paths
> > when _i386__ or __x86_64__ are defined. resctrl is an exception.
> >
> > Fix the problem by defining __cpuid_count() only when __i386__ or
> > __x86_64__ are defined in kselftest.h and changing resctrl to call
> > __cpuid_count() only when __i386__ or __x86_64__ are defined.
> >
> > 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:326:6:
> > ../kselftest.h:74:9: error: impossible constraint in ‘asm’
> >     74 |         __asm__ __volatile__ ("cpuid\n\t"                               \
> >        |         ^~~~~~~
> > cat_test.c:304:17: note: in expansion of macro ‘__cpuid_count’
> >    304 |                 __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:306:17: note: in expansion of macro ‘__cpuid_count’
> >    306 |                 __cpuid_count(0x10, 2, eax, ebx, ecx, edx);
> >
> > Reported-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
> > Reported-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> > Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
> LGTM
> Reviewed-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>

Thank you for the review and finding the problem to begin with.
Much appreciated.

> ...
> > diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
> > index 742782438ca3..ae3f0fa5390b 100644
> > --- a/tools/testing/selftests/resctrl/cat_test.c
> > +++ b/tools/testing/selftests/resctrl/cat_test.c
> > @@ -290,12 +290,12 @@ static int cat_run_test(const struct resctrl_test *test, const struct user_param
> >   
> >   static bool arch_supports_noncont_cat(const struct resctrl_test *test)
> >   {
> > -	unsigned int eax, ebx, ecx, edx;
> > -
> >   	/* AMD always supports non-contiguous CBM. */
> >   	if (get_vendor() == ARCH_AMD)
> >   		return true;
> >   
> > +#if defined(__i386__) || defined(__x86_64__) /* arch */
> > +	unsigned int eax, ebx, ecx, edx;
> >   	/* Intel support for non-contiguous CBM needs to be discovered. */
> >   	if (!strcmp(test->resource, "L3"))
> >   		__cpuid_count(0x10, 1, eax, ebx, ecx, edx);
> > @@ -305,6 +305,8 @@ static bool arch_supports_noncont_cat(const struct resctrl_test *test)
> >   		return false;
> >   
> >   	return ((ecx >> 3) & 1);
> > +#endif /* end arch */
> > +	return false;
> nit: empty line before return

Will do.

> >   }
> >   
> >   static int noncont_cat_run_test(const struct resctrl_test *test,

thanks,
-- Shuah