linux-kernel - Re: [PATCH v2 3/3] selftests/resctrl: Fix non-contiguous CBM check for Hygon

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Message-ID: <8ae52291-27e8-4614-9d27-b497ec22574d@intel.com>
Date: Fri, 5 Dec 2025 13:30:23 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Fenghua Yu <fenghuay@...dia.com>, Xiaochen Shen
	<shenxiaochen@...n-hieco.net>, <tony.luck@...el.com>, <bp@...en8.de>,
	<shuah@...nel.org>, <skhan@...uxfoundation.org>
CC: <babu.moger@....com>, <james.morse@....com>, <Dave.Martin@....com>,
	<x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] selftests/resctrl: Fix non-contiguous CBM check
 for Hygon

Hi Fenghua,

On 12/5/25 11:39 AM, Fenghua Yu wrote:
> 
> 
> On 12/5/25 01:25, Xiaochen Shen wrote:
>> The resctrl selftest currently fails on Hygon CPUs that always supports
>> non-contiguous CBM, printing the error:
>>
>>    "# Hardware and kernel differ on non-contiguous CBM support!"
>>
>> This occurs because the arch_supports_noncont_cat() function lacks
>> vendor detection for Hygon CPUs, preventing proper identification of
>> their non-contiguous CBM capability.
>>
>> Fix this by adding Hygon vendor ID detection to
>> arch_supports_noncont_cat().
>>
>> Signed-off-by: Xiaochen Shen <shenxiaochen@...n-hieco.net>
>> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
>> ---
>> Maintainer note:
>> Even though this is a fix it is not a candidate for backport since it is
>> based on another patch series (x86/resctrl: Fix Platform QoS issues for
>> Hygon) which is in process of being added to resctrl.
>>
>>   tools/testing/selftests/resctrl/cat_test.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
>> index 94cfdba5308d..59a0f80fdc5a 100644
>> --- a/tools/testing/selftests/resctrl/cat_test.c
>> +++ b/tools/testing/selftests/resctrl/cat_test.c
>> @@ -290,8 +290,8 @@ 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)
>>   {
>> -    /* AMD always supports non-contiguous CBM. */
>> -    if (get_vendor() == ARCH_AMD)
>> +    /* AMD and Hygon always supports non-contiguous CBM. */
>> +    if (get_vendor() == ARCH_AMD || get_vendor() == ARCH_HYGON)
> 
> nit. Better to avoid call get_vendor() twice (or even more in the future)?

Are you perhaps referring to detect_vendor()? detect_vendor() does the actual digging to
determine the vendor ID and is indeed called just once by get_vendor(). In subsequent calls 
get_vendor() just returns the static ID.

Reinette