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Wed, 13 Nov 2024 16:27:26 +0000 Message-ID: <9152f296-3f81-438d-8dc8-3c0bc60ea4b6@intel.com> Date: Wed, 13 Nov 2024 17:27:20 +0100 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/3] x86/smp native_play_dead: Prefer cpuidle_play_dead() over mwait_play_dead() To: Peter Zijlstra , "Gautham R. Shenoy" CC: "Rafael J. Wysocki" , Patryk Wlazlyn , , , , , , References: <20241108122909.763663-1-patryk.wlazlyn@linux.intel.com> <20241108122909.763663-3-patryk.wlazlyn@linux.intel.com> <20241112114743.GQ22801@noisy.programming.kicks-ass.net> <20241112145618.GR22801@noisy.programming.kicks-ass.net> <20241113162222.GA24625@noisy.programming.kicks-ass.net> Content-Language: en-US From: "Wysocki, Rafael J" In-Reply-To: <20241113162222.GA24625@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BE1P281CA0029.DEUP281.PROD.OUTLOOK.COM (2603:10a6:b10:15::19) To MW5PR11MB5810.namprd11.prod.outlook.com (2603:10b6:303:192::22) Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MW5PR11MB5810:EE_|SJ0PR11MB8270:EE_ X-MS-Office365-Filtering-Correlation-Id: 98b13225-9d05-4503-5b58-08dd04000f48 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024; 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Shenoy wrote: > >> How about something like this (completely untested) >> >> ---------------------x8---------------------------------------------------- >> >> diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c >> index f3ffd0a3a012..bd611771fa6c 100644 >> --- a/arch/x86/kernel/acpi/cstate.c >> +++ b/arch/x86/kernel/acpi/cstate.c >> @@ -215,6 +215,24 @@ void __cpuidle acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx) >> } >> EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_enter); >> >> +static int acpi_processor_ffh_play_dead(struct acpi_processor_cx *cx) >> +{ >> + unsigned int cpu = smp_processor_id(); >> + struct cstate_entry *percpu_entry; >> + >> + /* >> + * This is ugly. But AMD processors don't prefer MWAIT based >> + * C-states when processors are offlined. >> + */ >> + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || >> + boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) >> + return -ENODEV; > Are there AMD systems with FFh idle states at all? I don't know. > Also, I don't think this works right, the loop in cpuidle_play_dead() > will terminate on this, and not try a shallower state which might have > IO/HLT on. I think you are right. >> + >> + percpu_entry = per_cpu_ptr(cpu_cstate_entry, cpu); >> + return mwait_play_dead_with_hints(percpu_entry->states[cx->index].eax); >> +} >> +EXPORT_SYMBOL_GPL(acpi_processor_ffh_play_dead);