linux-kernel - Re: [PATCH V1 01/13] selftests/resctrl: Fix feature detection

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Message-ID: <d0409729-b546-f0b9-4944-cbe5c9a74f76@intel.com>
Date:   Mon, 9 Mar 2020 15:33:57 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "Luck, Tony" <tony.luck@...el.com>,
        "babu.moger@....com" <babu.moger@....com>,
        "james.morse@....com" <james.morse@....com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V1 01/13] selftests/resctrl: Fix feature detection

Hi Sai,

On 3/9/2020 3:22 PM, Prakhya, Sai Praneeth wrote:
> Hi Reinette,
> 
>> -----Original Message-----
>> From: Reinette Chatre <reinette.chatre@...el.com>
>> Sent: Monday, March 9, 2020 2:45 PM
>> On 3/6/2020 7:40 PM, Sai Praneeth Prakhya wrote:

[SNIP]

>> Please note that this is only a partial fix. The current feature detection relies on
>> the feature flags found in /proc/cpuinfo. Quirks and kernel boot parameters are
>> not taken into account. This fix only addresses the parsing of feature flags. If a
>> feature has been disabled via kernel boot parameter or quirk then the resctrl
>> tests would still attempt to run the test for it.
> 
> That's a good point and makes sense to me. I think we could fix it in two ways
> 1. grep for strings in dmesg but that will still leave ambiguity in deciding b/w mbm and cqm because kernel prints "resctrl: L3 monitoring detected" for both the features
> 2. Check in "info" directory
> 	a. For cat_l3, we could search for info/L3
> 	b. For mba, we could search for info/MB
> 	c. For cqm and mbm, we could search for specified string in info/L3_MON/mon_features
> 
> I think option 2 might be better because it can handle all cases, please let me know what you think.

I agree. For the reasons you mention and also that (1) may not be
possible if the loglevel prevents those lines from being printed.

Reinette