linux-kernel - Re: [PATCH] selftests:resctrl: Fix build failure on archs without __cpuid

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Message-ID: <ad3d035e-be82-44c4-a850-a33889fcf717@collabora.com>
Date: Fri, 6 Sep 2024 12:35:14 +0500
From: Muhammad Usama Anjum <Usama.Anjum@...labora.com>
To: Shuah Khan <skhan@...uxfoundation.org>, shuah@...nel.org,
 fenghua.yu@...el.com, reinette.chatre@...el.com,
 ilpo.jarvinen@...ux.intel.com
Cc: Usama.Anjum@...labora.com, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests:resctrl: Fix build failure on archs without
 __cpuid_count()

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@...labora.com>
> Reported-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
LGTM
Reviewed-by: Muhammad Usama Anjum <usama.anjum@...labora.com>

...
> 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

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

-- 
BR,
Muhammad Usama Anjum