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Message-ID: <2ec50632-15ae-44c3-9851-02660584dd05@linuxfoundation.org>
Date: Wed, 18 Oct 2023 13:07:28 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
Reinette Chatre <reinette.chatre@...el.com>,
Shuah Khan <shuah@...nel.org>
Cc: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>,
LKML <linux-kernel@...r.kernel.org>,
linux-kselftest@...r.kernel.org, Fenghua Yu <fenghua.yu@...el.com>,
Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v2 1/1] selftests/resctrl: Fix MBM test failure when MBA
unavailable
On 10/18/23 02:10, Ilpo Järvinen wrote:
> On Wed, 18 Oct 2023, Ilpo Järvinen wrote:
>
>> Commit 20d96b25cc4c ("selftests/resctrl: Fix schemata write error
>> check") exposed a problem in feature detection logic in MBM selftest.
>> If schemata does not support MB:x=x entries, the schemata write to
>> initialize 100% memory bandwidth allocation in mbm_setup() will now
>> fail with -EINVAL due to the error handling corrected by the commit
>> 20d96b25cc4c ("selftests/resctrl: Fix schemata write error check").
>> That commit just uncovers the failed write, it is not wrong itself.
>>
>> If MB:x=x is not supported by schemata, it is safe to assume 100%
>> memory bandwidth is always set. Therefore, the previously ignored error
>> does not make the MBM test itself wrong.
>>
>> Restore the previous behavior of MBM test by checking MB support before
>> attempting to write it into schemata which results in behavior
>> equivalent to ignoring the write error.
>>
>> Fixes: 20d96b25cc4c ("selftests/resctrl: Fix schemata write error check")
>> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
>> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
>> ---
>
> It seems it's too early morning for me so I entirely forgot to describe
> the changes I made... doh. So here it is (nothing earth-shattering here
> really):
>
> v2:
> - Make checkpatch --strict happy.
> - Remove () that --strict called "extra".
> - Duplicate the referenced commit description in the changelog
> to follow the commit formatting guidelines.
> - Alter the wording at one of the references into the commit
> 20d96b25cc4c in order to avoid having to copy the description
> there too.
> - Added Reinette's rev-by.
>
Thank you. Applied to linux-kselftest next for Linux 6.7-rc1
thanks,
-- Shuah
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