linux-kernel - Re: [PATCH v2 25/26] selftests/resctrl: Get domain id from cache id

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Date:   Tue, 28 Nov 2023 14:22:40 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        <linux-kselftest@...r.kernel.org>, Shuah Khan <shuah@...nel.org>,
        "Shaopeng Tan" <tan.shaopeng@...fujitsu.com>,
        Maciej Wieczór-Retman 
        <maciej.wieczor-retman@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>
CC:     <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 25/26] selftests/resctrl: Get domain id from cache id

Hi Ilpo,

On 11/20/2023 3:13 AM, Ilpo Järvinen wrote:
> Domain id is acquired differently depending on CPU. AMD tests use id
> from L3 cache, whereas CPUs from other vendors base the id on topology
> package id. In order to support L2 CAT test, this has to be
> generalized.
> 
> The driver side code seems to get the domain ids from cache ids so the
> approach used by the AMD branch seems to match the kernel-side code. It
> will also work with L2 domain IDs as long as the cache level is
> generalized.
> 
> Using the topology id was always fragile due to mismatch with the
> kernel-side way to acquire the domain id. It got incorrect domain id,
> e.g., when Cluster-on-Die (CoD) is enabled for CPU (but CoD is not well
> suited for resctrl in the first place so it has not been a big issue if
> tests don't work correctly with it).
> 
> Taking all the above into account, generalize acquiring the domain id
> by taking it from the cache id and do not hard-code the cache level.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---

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

Reinette