linux-kernel - Re: [PATCH v7 24/24] x86/resctrl: Introduce interface to modify assignment states of the groups

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Message-ID: <ca7b1d14-e37d-5f0d-9371-32d8506e51eb@amd.com>
Date: Thu, 3 Oct 2024 20:11:54 -0500
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, 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, seanjc@...gle.com,
 jmattson@...gle.com, leitao@...ian.org, jpoimboe@...nel.org,
 rick.p.edgecombe@...el.com, kirill.shutemov@...ux.intel.com,
 jithu.joseph@...el.com, kai.huang@...el.com, kan.liang@...ux.intel.com,
 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 24/24] x86/resctrl: Introduce interface to modify
 assignment states of the groups

Hi Reinette,

On 10/2/2024 1:19 PM, Reinette Chatre wrote:
> Hi Babu,
> 
> On 9/27/24 10:47 AM, Moger, Babu wrote:
>> On 9/19/2024 12:59 PM, Reinette Chatre wrote:
>>> On 9/4/24 3:21 PM, Babu Moger wrote:
> 
>>>> v7: Simplified the parsing (strsep(&token, "//") in rdtgroup_mbm_assign_control_write().
>>>>       Added mutex lock in rdtgroup_mbm_assign_control_write() while processing.
>>>>       Renamed rdtgroup_find_grp to rdtgroup_find_grp_by_name.
>>>>       Fixed rdtgroup_str_to_mon_state to return error for invalid flags.
>>>>       Simplified the calls rdtgroup_assign_cntr by merging few functions earlier.
>>>>       Removed ABMC reference in FS code.
>>>>       Reinette commented about handling the combination of flags like 'lt_' and '_lt'.
>>>>       Not sure if we need to change the behaviour here. Processed them sequencially right now.
>>>>       Users have the liberty to pass the flags. Restricting it might be a problem later.
>>>
>>> Could you please give an example of what problem may be encountered later? An assignment
>>> like "domain=_lt" seems like a contradiction to me since user space essentially asks
>>> for "None of the MBM events" as well as "MBM total event" and "MBM local event".
>>
>> I agree it is contradiction. But user is the one who decides to do that. I think we should allow it. Also, there is some value to it as well.
>>
>> "domain=_lt" This will also reset the counters if the total and local events are assigned earlier this action.
> 
> The last sentence is not clear to me. Could you please elaborate what
> you mean with "are assigned earlier this action"?
>

I think I confused you here. "domain=_lt" is equivalent to "domain=lt". 
  My reasoning is handling all the combination in the code adds code 
complexity and leave it the user what he wants to do.
- Babu Moger