linux-kernel - Re: [RFC PATCH v3 05/17] x86/resctrl: Introduce the interface to display the assignment state

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Message-ID: <4bcb0c46-458a-4ce9-a184-d3054a6ee26e@intel.com>
Date: Tue, 7 May 2024 13:32:08 -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>,
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	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: Re: [RFC PATCH v3 05/17] x86/resctrl: Introduce the interface to
 display the assignment state

Hi Babu,

On 5/7/2024 9:28 AM, Moger, Babu wrote:
> On 5/3/24 18:28, Reinette Chatre wrote:
>> On 3/28/2024 6:06 PM, Babu Moger wrote:

>>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
>>> index 735b449039c1..48d1957ea5a3 100644
>>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>>> @@ -1058,8 +1058,10 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
>>>  						 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
>>>  		}
>>>  
>>> -		if (resctrl_arch_has_abmc(r))
>>> +		if (resctrl_arch_has_abmc(r)) {
>>>  			r->mbm_assign_capable = ABMC_ASSIGN;
>>> +			resctrl_file_fflags_init("mbm_assign", RFTYPE_MON_INFO);
>>
>> I think this will need some more thought when considering the fs/arch split.
>> The architecture can be expected to set r->mbm_assign_capable as above but
>> having the architecture meddle with the fs flags does not seem like the right
>> thing to do. I think that RFTYPE_MON_INFO may not be accessible to arch code
>> anyway.
> 
> It is accessible to both arch and fs code per latest code.
> https://lore.kernel.org/lkml/20240426150904.8854-33-Dave.Martin@arm.com/

v2 of MPAM was posted without completing discussion of v1 nor addressing
all feedback.

Please read discussions surrounding #3 and #30 of v1. Note in particular suggestion
in [1] to keep RF flags internal to FS code. 

If MPAM chooses to submit new versions without completing discussions then
I have no problem letting ABMC proceed to build on what is resctrl at this time
and adding this to the pile of things MPAM needs to address during fs/arch split.

Reinette

[1] https://lore.kernel.org/lkml/b2595743-c7dc-4946-884f-ff159bc4865e@intel.com/