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Message-ID: <c96cdf6a-02a8-4ee2-91f5-e4329015e276@intel.com>
Date: Thu, 11 Apr 2024 10:39:06 -0700
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v1 17/31] x86/resctrl: Move mbm_cfg_mask to struct
 rdt_resource
To: Dave Martin <Dave.Martin@arm.com>
CC: James Morse <james.morse@arm.com>, <x86@kernel.org>,
	<linux-kernel@vger.kernel.org>, Fenghua Yu <fenghua.yu@intel.com>, "Thomas
 Gleixner" <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "Borislav
 Petkov" <bp@alien8.de>, H Peter Anvin <hpa@zytor.com>, Babu Moger
	<Babu.Moger@amd.com>, <shameerali.kolothum.thodi@huawei.com>, "D Scott
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	<lcherian@marvell.com>, <bobo.shaobowang@huawei.com>,
	<tan.shaopeng@fujitsu.com>, <baolin.wang@linux.alibaba.com>, Jamie Iles
	<quic_jiles@quicinc.com>, Xin Hao <xhao@linux.alibaba.com>,
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	David Hildenbrand <david@redhat.com>, Rex Nie <rex.nie@jaguarmicro.com>
References: <20240321165106.31602-1-james.morse@arm.com>
 <20240321165106.31602-18-james.morse@arm.com>
 <966b7b32-6600-4b1f-9535-0298fedd57a7@intel.com>
 <Zhfwzh4sHvTYyTJ1@e133380.arm.com>
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From: Reinette Chatre <reinette.chatre@intel.com>
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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@arm.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