Message-ID: <c23356c7-3af7-0aba-18b6-2e53ce18a164@intel.com>
Date:   Fri, 12 Nov 2021 10:00:23 -0800
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Subject: Re: [PATCH] selftests/resctrl: Skip MBM&CMT tests when Intel Sub-NUMA
Content-Language: en-US
To:     Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Shuah Khan <shuah@kernel.org>
CC:     <linux-kernel@vger.kernel.org>, <linux-kselftest@vger.kernel.org>
References: <20211110082734.3184985-1-tan.shaopeng@jp.fujitsu.com>
From:   Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <20211110082734.3184985-1-tan.shaopeng@jp.fujitsu.com>
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Hi,

On 11/10/2021 12:27 AM, Shaopeng Tan wrote:
> From: "Tan, Shaopeng" <tan.shaopeng@jp.fujitsu.com>
> 
> When the Intel Sub-NUMA Clustering(SNC) feature is enabled,
> the CMT and MBM counters may not be accurate.
> In this case, skip MBM&CMT tests.
> 
> Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> ---
> Hello,
> 
> According to the Intel RDT reference Manual,
> when the sub-numa clustering feature is enabled, the CMT and MBM counters may not be accurate.
> When running CMT tests and MBM tests on Intel processor, the result is "not ok".
> So, fix it to skip the CMT & MBM test When the Intel Sub-NUMA Clustering(SNC) feature is enabled.
> 

It is not clear to me which exact document you refer to but I did find a 
RDT reference manual at the link below that describes the problem you 
mention:
https://www.intel.com/content/dam/develop/external/us/en/documents/180115-intel-rdtcascadelake-serverreferencemanual-806717.pdf

What is not mentioned in your description is that this is a hardware 
errata so the test is expected to fail on these systems and I find that 
disabling the test for all systems based on this hardware errata is too 
drastic.

Reinette