linux-kernel - Re: [PATCH v1 17/31] x86/resctrl: Move mbm_cfg_mask to struct rdt

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Date: Thu, 11 Apr 2024 10:39:06 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Dave Martin <Dave.Martin@....com>
CC: James Morse <james.morse@....com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>, Fenghua Yu <fenghua.yu@...el.com>, "Thomas
 Gleixner" <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "Borislav
 Petkov" <bp@...en8.de>, H Peter Anvin <hpa@...or.com>, Babu Moger
	<Babu.Moger@....com>, <shameerali.kolothum.thodi@...wei.com>, "D Scott
 Phillips OS" <scott@...amperecomputing.com>, <carl@...amperecomputing.com>,
	<lcherian@...vell.com>, <bobo.shaobowang@...wei.com>,
	<tan.shaopeng@...itsu.com>, <baolin.wang@...ux.alibaba.com>, Jamie Iles
	<quic_jiles@...cinc.com>, Xin Hao <xhao@...ux.alibaba.com>,
	<peternewman@...gle.com>, <dfustini@...libre.com>, <amitsinght@...vell.com>,
	David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>
Subject: Re: [PATCH v1 17/31] x86/resctrl: Move mbm_cfg_mask to struct
 rdt_resource

Hi Dave,

On 4/11/2024 7:16 AM, Dave Martin wrote:
> On Mon, Apr 08, 2024 at 08:21:24PM -0700, Reinette Chatre wrote:
>> Hi James,
>>
>> On 3/21/2024 9:50 AM, James Morse wrote:
>>> The mbm_cfg_mask field lists the bits that user-space can set when
>>> configuring an event. This value is output via the last_cmd_status
>>> file.
>>>
>>> Once the filesystem parts of resctrl are moved to live in /fs/, the
>>> struct rdt_hw_resource is inaccessible to the filesystem code. Because
>>> this value is output to user-space, it has to be accessible to the
>>> filesystem code.
>>>
>>> Move it to struct rdt_resource.
>>>
>>> Signed-off-by: James Morse <james.morse@....com>
>>
>> ..
>>
>>> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
>>> index 975b80102fbe..8a7367d1ce45 100644
>>> --- a/include/linux/resctrl.h
>>> +++ b/include/linux/resctrl.h
>>> @@ -140,6 +140,8 @@ struct resctrl_membw {
>>>   * @format_str:		Per resource format string to show domain value
>>>   * @evt_list:		List of monitoring events
>>>   * @fflags:		flags to choose base and info files
>>> + * @mbm_cfg_mask:	Bandwidth sources that can be tracked when Bandwidth
>>> + *			Monitoring Event Configuration (BMEC) is supported.
> 
> [...]
> 
>> Reinette
>>
>> BMEC is an AMD term. If MPAM is planning to use this member then this comment
>> should be made generic.
> 
> MPAM can (at least) filter reads and/or writes, and it looks like James
> is expecting to support this.
> 
> However, it probably does make sense to keep the comments neutral in a
> common header.
> 
> Would the following work?
> 
> 	* @ mbm_cfg_mask:	Arch-specific event configuration flags
> 
> 
> 
> I think that's broad enough to cover all bases, but I'll wait for your
> response.

Since this is exposed to user space, ideally all architectures would use
the same bits to mean the same thing. I assumed that is what James intended
by placing the existing (AMD BMEC) bits in the global resctrl_types.h.

Reinette