linux-kernel - Re: [PATCH v7 15/24] x86/resctrl: Implement resctrl_arch_assign

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Message-ID: <666aa4ae-141f-4625-909a-d905e8f1c66d@amd.com>
Date: Mon, 23 Sep 2024 16:03:46 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.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 15/24] x86/resctrl: Implement resctrl_arch_assign_cntr
 to assign a counter with ABMC

Hi Reinette,

On 9/19/24 12:13, Reinette Chatre wrote:
> Hi Babu,
> 
> In subject, please use "()" for a function.

Sure.

> 
> On 9/4/24 3:21 PM, Babu Moger wrote:
>> +/*
>> + * Send an IPI to the domain to assign the counter to RMID, event pair.
>> + */
>> +int resctrl_arch_assign_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>> +			     enum resctrl_event_id evtid, u32 rmid, u32 closid,
>> +			     u32 cntr_id, bool assign)
> 
> Looking ahead this is also called when config of existing assigned counter is
> changed. Should this thus perhaps be resctrl_arch_config_cntr()? 

We have a matching resctrl_arch_assign_cntr() and
resctrl_arch_unassign_cntr() pair.

If we change resctrl_arch_config_cntr() then we need to change
resctrl_arch_unassign_cntr to resctrl_arch_unconfig_cntr().

Should we change both?


> 
>> +{
>> +	struct rdt_hw_mon_domain *hw_dom = resctrl_to_arch_mon_dom(d);
>> +	union l3_qos_abmc_cfg abmc_cfg = { 0 };
>> +	struct arch_mbm_state *arch_mbm;
>> +
>> +	abmc_cfg.split.cfg_en = 1;
> 
> Just to confirm ... a counter remains "configured" from the hardware side whether it
> is assigned from resctrl perspective or not? It seems to me that once a counter is
> "unassigned" from resctrl perspective it needs no more context about that
> counter, yet it remains configured from hardware side?

That is correct.
When unassigned, we are setting cntr_en = 0, so there is no counting. But
in hardware perspective it is still configured.
-- 
Thanks
Babu Moger