linux-kernel - Re: [PATCH v9 10/13] x86/resctrl: Add sysfs interface to write mbm_total_bytes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 20 Dec 2022 09:32:01 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     "Moger, Babu" <Babu.Moger@....com>,
        "corbet@....net" <corbet@....net>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>
CC:     "fenghua.yu@...el.com" <fenghua.yu@...el.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "paulmck@...nel.org" <paulmck@...nel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "quic_neeraju@...cinc.com" <quic_neeraju@...cinc.com>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "damien.lemoal@...nsource.wdc.com" <damien.lemoal@...nsource.wdc.com>,
        "songmuchun@...edance.com" <songmuchun@...edance.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "jpoimboe@...nel.org" <jpoimboe@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "chang.seok.bae@...el.com" <chang.seok.bae@...el.com>,
        "pawan.kumar.gupta@...ux.intel.com" 
        <pawan.kumar.gupta@...ux.intel.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "daniel.sneddon@...ux.intel.com" <daniel.sneddon@...ux.intel.com>,
        "Das1, Sandipan" <Sandipan.Das@....com>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "james.morse@....com" <james.morse@....com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "eranian@...gle.com" <eranian@...gle.com>,
        "christophe.leroy@...roup.eu" <christophe.leroy@...roup.eu>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
        "quic_jiles@...cinc.com" <quic_jiles@...cinc.com>,
        "peternewman@...gle.com" <peternewman@...gle.com>
Subject: Re: [PATCH v9 10/13] x86/resctrl: Add sysfs interface to write
 mbm_total_bytes_config

Hi Babu,

On 12/19/2022 11:28 AM, Moger, Babu wrote:
> [AMD Official Use Only - General]
> 
> Hi Reinette,
> 
>> -----Original Message-----
>> From: Reinette Chatre <reinette.chatre@...el.com>
>> Sent: Thursday, December 15, 2022 12:25 PM
>> To: Moger, Babu <Babu.Moger@....com>; corbet@....net;
>> tglx@...utronix.de; mingo@...hat.com; bp@...en8.de
>> Cc: fenghua.yu@...el.com; dave.hansen@...ux.intel.com; x86@...nel.org;
>> hpa@...or.com; paulmck@...nel.org; akpm@...ux-foundation.org;
>> quic_neeraju@...cinc.com; rdunlap@...radead.org;
>> damien.lemoal@...nsource.wdc.com; songmuchun@...edance.com;
>> peterz@...radead.org; jpoimboe@...nel.org; pbonzini@...hat.com;
>> chang.seok.bae@...el.com; pawan.kumar.gupta@...ux.intel.com;
>> jmattson@...gle.com; daniel.sneddon@...ux.intel.com; Das1, Sandipan
>> <Sandipan.Das@....com>; tony.luck@...el.com; james.morse@....com;
>> linux-doc@...r.kernel.org; linux-kernel@...r.kernel.org;
>> bagasdotme@...il.com; eranian@...gle.com; christophe.leroy@...roup.eu;
>> jarkko@...nel.org; adrian.hunter@...el.com; quic_jiles@...cinc.com;
>> peternewman@...gle.com
>> Subject: Re: [PATCH v9 10/13] x86/resctrl: Add sysfs interface to write
>> mbm_total_bytes_config
>>
>> Hi Babu,
>>
>> On 12/1/2022 7:37 AM, Babu Moger wrote:

...

>>> +	/*
>>> +	 * When an Event Configuration is changed, the bandwidth counters
>>> +	 * for all RMIDs and Events will be cleared by the hardware. The
>>> +	 * hardware also sets MSR_IA32_QM_CTR.Unavailable (bit 62) for
>>> +	 * every RMID on the next read to any event for every RMID.
>>> +	 * Subsequent reads will have MSR_IA32_QM_CTR.Unavailable (bit 62)
>>> +	 * cleared while it is tracked by the hardware. Clear the
>>> +	 * mbm_local and mbm_total counts for all the RMIDs.
>>> +	 */
>>> +	resctrl_arch_reset_rmid_all(r, d);
>>
>> If I understand correctly the expectation is that when user space read counters
>> (via mon_data files) right after the configuration was changed then this read
>> will return "Unavailable" and then the next read will return data.
>>
>> If this is the case then I think a snippet about this user experience would be
>> helpful to add to the documentation.
> 
> Ok.  How about this in the documentation?
> 
> "When an event configuration is changed, the bandwidth counters for all the RMIDs and the events will be cleared for that domain.
> The next read for every RMID will report "Unavailable" and subsequent reads will report the valid value."
> 
> 

Thinking about this more ... why are the counters for all eventids cleared
when only one eventid's configuration is changed?

Reinette