linux-kernel - Re: [PATCH v9 21/26] x86/resctrl: Report "Unassigned" for MBM events in mbm_cntr

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Message-ID: <ae12f5d7-2f38-4f38-ab19-0875bd393443@intel.com>
Date: Mon, 18 Nov 2024 09:39:32 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <fenghua.yu@...el.com>, <x86@...nel.org>, <hpa@...or.com>,
	<thuth@...hat.com>, <paulmck@...nel.org>, <rostedt@...dmis.org>,
	<akpm@...ux-foundation.org>, <xiongwei.song@...driver.com>,
	<pawan.kumar.gupta@...ux.intel.com>, <daniel.sneddon@...ux.intel.com>,
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	<maciej.wieczor-retman@...el.com>, <eranian@...gle.com>,
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Subject: Re: [PATCH v9 21/26] x86/resctrl: Report "Unassigned" for MBM events
 in mbm_cntr_assign mode

Hi Babu,

On 10/29/24 4:21 PM, Babu Moger wrote:
> In mbm_cntr_assign mode, the hardware counter should be assigned to read
> the MBM events.
> 
> Report "Unassigned" in case the user attempts to read the events without
> assigning the counter.
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> v9: Used is_mbm_event() to check the event type.
>     Minor user documentation update.
> 
> v8: Used MBM_EVENT_ARRAY_INDEX to get the index for the MBM event.
>     Documentation update to make the text generic.
> 
> v7: Moved the documentation under "mon_data".
>     Updated the text little bit.
> 
> v6: Added more explaination in the resctrl.rst
>     Added checks to detect "Unassigned" before reading RMID.
> 
> v5: New patch.
> ---
>  Documentation/arch/x86/resctrl.rst        | 10 ++++++++++
>  arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 12 +++++++++++-
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 2bc58d974934..864fc004d646 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -430,6 +430,16 @@ When monitoring is enabled all MON groups will also contain:
>  	for the L3 cache they occupy). These are named "mon_sub_L3_YY"
>  	where "YY" is the node number.
>  
> +	When supported the 'mbm_cntr_assign' mode allows users to assign a

Could you please do through the documentation changes and make all the quote
usage consistent with existing styles? For example, in this series "mbm_cntr_assign"
is used in doc in various ways ... within double quotes, within single quotes, as
well as without any quotes.

> +	counter to mon_hw_id, event pair enabling bandwidth monitoring for
> +	as long as the counter remains assigned. The hardware will continue
> +	tracking the assigned mon_hw_id until the user manually unassigns
> +	it, ensuring that counters are not reset during this period. With
> +	a limited number of counters, the system may run out of assignable
> +	counters. In that case, MBM event counters will return "Unassigned"

Please review style for all quote usage, for example, "Unassigned" above is
also not consistent.

> +	when the event is read. Users must manually assign a counter to read
> +	the events.
> +
Reinette