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

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Message-ID: <2af94be4-95f1-48c9-a552-88352cd5d44d@intel.com>
Date: Thu, 5 Sep 2024 13:45:33 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Shuah Khan <skhan@...uxfoundation.org>, <shuah@...nel.org>,
	<fenghua.yu@...el.com>, <ilpo.jarvinen@...ux.intel.com>,
	<usama.anjum@...labora.com>
CC: <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 very much for looking into this.

On 9/5/24 11:02 AM, 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);
> 

If needing to know where this fix is needed, there can be a:
Fixes: ae638551ab64 ("selftests/resctrl: Add non-contiguous CBMs CAT test")

> Reported-by: Muhammad Usama Anjum <usama.anjum@...labora.com>

Perhaps:
Closes: https://lore.kernel.org/lkml/20240809071059.265914-1-usama.anjum@collabora.com/

> Reported-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
> ---
>   tools/testing/selftests/kselftest.h        | 2 ++
>   tools/testing/selftests/resctrl/cat_test.c | 6 ++++--
>   2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h
> index b8967b6e29d5..e195ec156859 100644
> --- a/tools/testing/selftests/kselftest.h
> +++ b/tools/testing/selftests/kselftest.h
> @@ -61,6 +61,7 @@
>   #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
>   #endif
>   
> +#if defined(__i386__) || defined(__x86_64__) /* arch */
>   /*
>    * gcc cpuid.h provides __cpuid_count() since v4.4.
>    * Clang/LLVM cpuid.h provides  __cpuid_count() since v3.4.0.
> @@ -75,6 +76,7 @@
>   			      : "=a" (a), "=b" (b), "=c" (c), "=d" (d)	\
>   			      : "0" (level), "2" (count))
>   #endif
> +#endif /* end arch */
>   
>   /* define kselftest exit codes */
>   #define KSFT_PASS  0
> 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;
>   }
>   
>   static int noncont_cat_run_test(const struct resctrl_test *test,

Thank you very much.

Acked-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette