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Date: Tue, 5 Mar 2024 08:48:51 -0800
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v4 1/2] x86/resctrl: Pass domain to target CPU
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To: "Luck, Tony" <tony.luck@intel.com>, "Yu, Fenghua" <fenghua.yu@intel.com>,
	Peter Newman <peternewman@google.com>, Jonathan Corbet <corbet@lwn.net>,
	Shuah Khan <skhan@linuxfoundation.org>, "x86@kernel.org" <x86@kernel.org>
CC: Shaopeng Tan <tan.shaopeng@fujitsu.com>, James Morse
	<james.morse@arm.com>, Jamie Iles <quic_jiles@quicinc.com>, Babu Moger
	<babu.moger@amd.com>, Randy Dunlap <rdunlap@infradead.org>, Drew Fustini
	<dfustini@baylibre.com>, "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>, "linux-doc@vger.kernel.org"
	<linux-doc@vger.kernel.org>, "patches@lists.linux.dev"
	<patches@lists.linux.dev>
References: <20240228112215.8044-tony.luck@intel.com>
 <20240228193717.8170-1-tony.luck@intel.com>
 <12766261-26b2-4aa4-a735-c2380c4963fd@intel.com>
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From: Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <SJ1PR11MB6083C8DF1FD451CD43D6726FFC222@SJ1PR11MB6083.namprd11.prod.outlook.com>
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Hi Tony,

On 3/5/2024 8:37 AM, Luck, Tony wrote:
>> If I understand correctly that would always look for a valid "cpu"
>> even when none is needed. Not quite what I proposed but should
>> work. Just some wasted cycles in a non critical path. 
> 
> Reinette,
> 
> Sorry for misunderstanding. You are right. Assignment to msr_param.dom
> can also be deferred to the same point. Like this:
> 
>         list_for_each_entry(d, &r->domains, list) {
>                 hw_dom = resctrl_to_arch_dom(d);
>                 msr_param.res = NULL;
>                 for (t = 0; t < CDP_NUM_TYPES; t++) {
>                         cfg = &hw_dom->d_resctrl.staged_config[t];
>                         if (!cfg->have_new_ctrl)
>                                 continue;
> 
>                         idx = get_config_index(closid, t);
>                         if (cfg->new_ctrl == hw_dom->ctrl_val[idx])
>                                 continue;
>                         hw_dom->ctrl_val[idx] = cfg->new_ctrl;
> 
>                         if (!msr_param.res) {
>                                 msr_param.low = idx;
>                                 msr_param.high = msr_param.low + 1;
>                                 msr_param.res = r;
>                                 msr_param.dom = d;
>                                 cpu = cpumask_any(&d->cpu_mask);
>                         } else {
>                                 msr_param.low = min(msr_param.low, idx);
>                                 msr_param.high = max(msr_param.high, idx + 1);
>                         }
>                 }
>                 if (msr_param.res)
>                         smp_call_function_single(cpu, rdt_ctrl_update, &msr_param, 1);
>         }

This looks good to me. 

Thank you very much.

Reinette