linux-kernel - Re: [PATCH v7 09/24] x86/resctrl: Introduce bitmap mbm_cntr_free

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Message-ID: <175ac51f-62bc-481c-a31f-b1e372ac343a@intel.com>
Date: Mon, 23 Sep 2024 15:28:52 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: <babu.moger@....com>, <corbet@....net>, <fenghua.yu@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
	<yanjiewtw@...il.com>, <kim.phillips@....com>, <lukas.bulwahn@...il.com>,
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	<jpoimboe@...nel.org>, <rick.p.edgecombe@...el.com>,
	<kirill.shutemov@...ux.intel.com>, <jithu.joseph@...el.com>,
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	<daniel.sneddon@...ux.intel.com>, <pbonzini@...hat.com>,
	<sandipan.das@....com>, <ilpo.jarvinen@...ux.intel.com>,
	<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: Re: [PATCH v7 09/24] x86/resctrl: Introduce bitmap mbm_cntr_free_map
 to track assignable counters

Hi Babu,

On 9/23/24 11:33 AM, Moger, Babu wrote:
> Hi Reinette,
> 
> On 9/19/24 11:42, Reinette Chatre wrote:
>> Hi Babu,
>>
>> On 9/4/24 3:21 PM, Babu Moger wrote:
>>> Hardware provides a set of counters when mbm_cntr_assignable feature is
>>> supported. These counters are used for assigning the events in resctrl
>>> a group when the feature is enabled. The kernel must manage and track the
>>
>> The second sentence ("These counters ...") is difficult to parse.
> 
> How about?
> 
> Counters are used for assigning the events in resctrl group.

Apologies but I am just not able to parse this. How about: "These counters
are assigned to the MBM monitoring events of a MON group that needs to
be tracked."

...

>>> + */
>>> +static int mbm_cntrs_init(struct rdt_resource *r)
>>
>> Needs __init?
> 
> Did you mean to merge this with dom_data_init and don't have to have a
> separate function. Please clarify.

Here I was referring to the actual __init storage class attribute. Since
mbm_cntrs_init() is only called by __init code, it too should have the
__init storage class attribute.
I do expect that mbm_cntrs_init() will be called by dom_data_init() and
care should be taken when making this change since it seems that dom_data_init()
itself needs the __init storage class attribute. Looks like this was missed
by commit bd334c86b5d7 ("x86/resctrl: Add __init attribute to rdt_get_mon_l3_config()")

Reinette