From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DD154C02198 for ; Tue, 18 Feb 2025 14:12:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-ID:Date :Subject:CC:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=FGGTxpGEya+y3DCKSasDByHMsQJWfIB0xG5m7Wt2qrk=; b=Y9EjpFvZKvCf7m5cIpVEivBlF9 /n2xnAyAF5rz9sUXKHDNeUost9A0FEliyosefvvLAsvEU5dq7Q3RdfSrAGJRaFY+ElhgOR+f+BT/n lkCbz6/dZRdUAAUF6mchWUyCel9R4Gj4fEdF8HGhgKx5Klf+F/ZCV8HXv4Jj7B7k6zVkPpGADdu50 p5Kns7ZrViZNHf5ef4+yAfgjcRBpD4bKTnu61VViSlTOaKiw6oSlIywuk2pQChwRDkq7c/SC189yN rpReA+lJA4mIkyeX9uFqMOiQMoag7AF5TzlRRAm6R0jEri/QiYyZXMsBppzKMvJjlZjCqIhfqRmjf 3YB1OpZw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tkOKD-00000008S6d-2liQ; Tue, 18 Feb 2025 14:11:49 +0000 Received: from szxga05-in.huawei.com ([45.249.212.191]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tkOIi-00000008RiN-40Bh for linux-arm-kernel@lists.infradead.org; Tue, 18 Feb 2025 14:10:19 +0000 Received: from mail.maildlp.com (unknown [172.19.162.112]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4Yy1bB44KszMrc8; Tue, 18 Feb 2025 22:08:38 +0800 (CST) Received: from kwepemd200014.china.huawei.com (unknown [7.221.188.8]) by mail.maildlp.com (Postfix) with ESMTPS id 4A3491400D6; Tue, 18 Feb 2025 22:10:08 +0800 (CST) Received: from localhost.localdomain (10.50.165.33) by kwepemd200014.china.huawei.com (7.221.188.8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.34; Tue, 18 Feb 2025 22:10:07 +0800 From: Yicong Yang To: , , , , , , , , , , , CC: , , , , , , , , , , , , , Subject: [PATCH v11 1/4] cpu/SMT: Provide a default topology_is_primary_thread() Date: Tue, 18 Feb 2025 22:10:15 +0800 Message-ID: <20250218141018.18082-2-yangyicong@huawei.com> X-Mailer: git-send-email 2.31.0 In-Reply-To: <20250218141018.18082-1-yangyicong@huawei.com> References: <20250218141018.18082-1-yangyicong@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.50.165.33] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemd200014.china.huawei.com (7.221.188.8) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250218_061017_428713_68B1A6E2 X-CRM114-Status: GOOD ( 18.31 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Yicong Yang Currently if architectures want to support HOTPLUG_SMT they need to provide a topology_is_primary_thread() telling the framework which thread in the SMT cannot offline. However arm64 doesn't have a restriction on which thread in the SMT cannot offline, a simplest choice is that just make 1st thread as the "primary" thread. So just make this as the default implementation in the framework and let architectures like x86 that have special primary thread to override this function (which they've already done). There's no need to provide a stub function if !CONFIG_SMP or !CONFIG_HOTPLUG_SMT. In such case the testing CPU is already the 1st CPU in the SMT so it's always the primary thread. Reviewed-by: Jonathan Cameron Signed-off-by: Yicong Yang --- Pre questioned in v9 [1] whether this works on architectures not using CONFIG_GENERIC_ARCH_TOPOLOGY, See [2] for demonstration hacking on LoongArch VM and this also works. Architectures should use this on their own situation. [1] https://lore.kernel.org/linux-arm-kernel/427bd639-33c3-47e4-9e83-68c428eb1a7d@arm.com/ [2] https://lore.kernel.org/linux-arm-kernel/a5690fee-3019-f26c-8bad-1d95e388e877@huawei.com/ arch/powerpc/include/asm/topology.h | 1 + arch/x86/include/asm/topology.h | 2 +- include/linux/topology.h | 22 ++++++++++++++++++++++ 3 files changed, 24 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h index 16bacfe8c7a2..da15b5efe807 100644 --- a/arch/powerpc/include/asm/topology.h +++ b/arch/powerpc/include/asm/topology.h @@ -152,6 +152,7 @@ static inline bool topology_is_primary_thread(unsigned int cpu) { return cpu == cpu_first_thread_sibling(cpu); } +#define topology_is_primary_thread topology_is_primary_thread static inline bool topology_smt_thread_allowed(unsigned int cpu) { diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h index ec134b719144..6c79ee7c0957 100644 --- a/arch/x86/include/asm/topology.h +++ b/arch/x86/include/asm/topology.h @@ -229,11 +229,11 @@ static inline bool topology_is_primary_thread(unsigned int cpu) { return cpumask_test_cpu(cpu, cpu_primary_thread_mask); } +#define topology_is_primary_thread topology_is_primary_thread #else /* CONFIG_SMP */ static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; } static inline int topology_max_smt_threads(void) { return 1; } -static inline bool topology_is_primary_thread(unsigned int cpu) { return true; } static inline unsigned int topology_amd_nodes_per_pkg(void) { return 1; } #endif /* !CONFIG_SMP */ diff --git a/include/linux/topology.h b/include/linux/topology.h index 52f5850730b3..b3aba443c4eb 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -240,6 +240,28 @@ static inline const struct cpumask *cpu_smt_mask(int cpu) } #endif +#ifndef topology_is_primary_thread + +#define topology_is_primary_thread topology_is_primary_thread + +static inline bool topology_is_primary_thread(unsigned int cpu) +{ + /* + * On SMT hotplug the primary thread of the SMT won't be disabled. + * Architectures do have a special primary thread (e.g. x86) need + * to override this function. Otherwise just make the first thread + * in the SMT as the primary thread. + * + * The sibling cpumask of an offline CPU contains always the CPU + * itself for architectures using CONFIG_GENERIC_ARCH_TOPOLOGY. + * Other architectures should use this depend on their own + * situation. + */ + return cpu == cpumask_first(topology_sibling_cpumask(cpu)); +} + +#endif + static inline const struct cpumask *cpu_cpu_mask(int cpu) { return cpumask_of_node(cpu_to_node(cpu)); -- 2.24.0