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Wed, 25 Sep 2024 23:24:56 +0000 Received: from DM8PR10MB5416.namprd10.prod.outlook.com ([fe80::e085:31f:84d1:e51a]) by DM8PR10MB5416.namprd10.prod.outlook.com ([fe80::e085:31f:84d1:e51a%5]) with mapi id 15.20.8005.010; Wed, 25 Sep 2024 23:24:56 +0000 From: Ankur Arora To: linux-pm@vger.kernel.org, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, pbonzini@redhat.com, wanpengli@tencent.com, vkuznets@redhat.com, rafael@kernel.org, daniel.lezcano@linaro.org, peterz@infradead.org, arnd@arndb.de, lenb@kernel.org, mark.rutland@arm.com, harisokn@amazon.com, mtosatti@redhat.com, sudeep.holla@arm.com, cl@gentwo.org, misono.tomohiro@fujitsu.com, maobibo@loongson.cn, joao.m.martins@oracle.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com Subject: [PATCH v8 11/11] arm64: support cpuidle-haltpoll Date: Wed, 25 Sep 2024 16:24:25 -0700 Message-Id: <20240925232425.2763385-12-ankur.a.arora@oracle.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20240925232425.2763385-1-ankur.a.arora@oracle.com> References: <20240925232425.2763385-1-ankur.a.arora@oracle.com> X-ClientProxiedBy: MW2PR16CA0054.namprd16.prod.outlook.com (2603:10b6:907:1::31) To DM8PR10MB5416.namprd10.prod.outlook.com (2603:10b6:8:3f::19) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM8PR10MB5416:EE_|LV8PR10MB7943:EE_ X-MS-Office365-Filtering-Correlation-Id: ad64c0c1-981f-4f8c-ddc9-08dcddb9441f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|366016|1800799024; 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Also define ARCH_CPUIDLE_HALTPOLL to allow cpuidle-haltpoll to be selected. Haltpoll uses poll_idle() to do the actual polling. This in turn uses smp_cond_load*() to wait until there's a specific store to a cacheline. In the edge case -- no stores to the cacheline and no interrupt -- the event-stream provides the terminating condition ensuring we don't wait forever. But because the event-stream runs at a fixed frequency (configured at 10kHz) haltpoll might spend more time in the polling stage than specified by cpuidle_poll_time(). This would only happen in the last iteration, since overshooting the poll_limit means the governor will move out of the polling stage. Tested-by: Haris Okanovic Tested-by: Misono Tomohiro Signed-off-by: Ankur Arora Reviewed-by: Haris Okanovic Tested-by: Haris Okanovic Reviewed-by: Christoph Lameter (Ampere) --- arch/arm64/Kconfig | 6 ++++++ arch/arm64/include/asm/cpuidle_haltpoll.h | 24 +++++++++++++++++++++++ 2 files changed, 30 insertions(+) create mode 100644 arch/arm64/include/asm/cpuidle_haltpoll.h diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index ef9c22c3cff2..5fc99eba22b2 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -2415,6 +2415,12 @@ config ARCH_HIBERNATION_HEADER config ARCH_SUSPEND_POSSIBLE def_bool y +config ARCH_CPUIDLE_HALTPOLL + bool "Enable selection of the cpuidle-haltpoll driver" + help + cpuidle-haltpoll allows for adaptive polling based on + current load before entering the idle state. + endmenu # "Power management options" menu "CPU Power Management" diff --git a/arch/arm64/include/asm/cpuidle_haltpoll.h b/arch/arm64/include/asm/cpuidle_haltpoll.h new file mode 100644 index 000000000000..91f0be707629 --- /dev/null +++ b/arch/arm64/include/asm/cpuidle_haltpoll.h @@ -0,0 +1,24 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef _ARCH_HALTPOLL_H +#define _ARCH_HALTPOLL_H + +static inline void arch_haltpoll_enable(unsigned int cpu) { } +static inline void arch_haltpoll_disable(unsigned int cpu) { } + +static inline bool arch_haltpoll_want(bool force) +{ + /* + * Enabling haltpoll requires two things: + * + * - Event stream support to provide a terminating condition to the + * WFE in the poll loop. + * + * - KVM support for arch_haltpoll_enable(), arch_haltpoll_disable(). + * + * Given that the second is missing, only allow force loading for + * haltpoll. + */ + return force; +} +#endif