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 5DF0DCCD183 for ; Mon, 13 Oct 2025 20:35:36 +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-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=BBGFraA2r18snrtykXuSXO9gIBJ9e1axYh5bPV7np4Y=; b=n/wgwl98tTRs8q+A8/LEVAegIs POorst3OOTOLPueYD2b2kpGuJCRv853Fb7E0dQj2BU/xIcUdxrfOS56yiDBRuTtmxYFA7jJmKvNKq JEHwUTNxso84fPH0H7GZMBQRStTke3mUCqQDDWY0C1gbZsUXUTF33DBF99IbKt96PM2iyNgPDzfby PiK7W/H1/Nr4VtSSyDReDU2g0E32UFhcd8nnZhIV3LeGCdah8nFM0fVps34GVUMB/+Zg0oTx1ZT4U Ufca1g/0dn6tAex3KURCVyFR0Mre4RqGibIySjR5Tr/4ct3P1I8507rcnLZYocw9jYkvNgXWDKMG7 5tPG9uNg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8PGU-0000000EPla-1Fwv; Mon, 13 Oct 2025 20:35:30 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8PGQ-0000000EPil-3Q2P for linux-arm-kernel@lists.infradead.org; Mon, 13 Oct 2025 20:35:29 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 7B4B64079F; Mon, 13 Oct 2025 20:35:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F449C4CEF8; Mon, 13 Oct 2025 20:35:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760387726; bh=TCF8MVyq430j5XDUVoolby9dsM0WVQ59dd/A7DweIIA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=puNf58eHX8iqWcX4jZvJoV0HGrBTDxCWE15XDARtObLpMMvPRy+y0OstVhXwHQ7fV smjRbaQwXlOhyGu62k0J3ZKNFF8Z9wmsPYW5kXmhDQvYC6sF1F5JdQb7XTbwVZW5S0 Zt/yHfXLXhsTxeaN8S+H+auqeS8oizw+IOarobKVOzujEmr1QjfvzUs0BqICIIDDXL pGvdPObIsHFEAiS3kgMyvjdXl9zFRMAvkyTmw2EpLDOqyH3d8mqgV/XdWCkmoKbBmu a6Rg6jsQfpUS08mwcwK0iUDhWGkLgDfnbwngzO3gEWxXv25X+lXS95VuIpVGAFcigO Xo9mEZeO/fQ/Q== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Andrew Morton , Bjorn Helgaas , Catalin Marinas , Danilo Krummrich , "David S . Miller" , Eric Dumazet , Gabriele Monaco , Greg Kroah-Hartman , Ingo Molnar , Jakub Kicinski , Jens Axboe , Johannes Weiner , Lai Jiangshan , Marco Crivellari , Michal Hocko , Muchun Song , Paolo Abeni , Peter Zijlstra , Phil Auld , "Rafael J . Wysocki" , Roman Gushchin , Shakeel Butt , Simon Horman , Tejun Heo , Thomas Gleixner , Vlastimil Babka , Waiman Long , Will Deacon , cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH 27/33] sched/arm64: Move fallback task cpumask to HK_TYPE_DOMAIN Date: Mon, 13 Oct 2025 22:31:40 +0200 Message-ID: <20251013203146.10162-28-frederic@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251013203146.10162-1-frederic@kernel.org> References: <20251013203146.10162-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251013_133527_990308_2D22A889 X-CRM114-Status: GOOD ( 17.96 ) 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 When none of the allowed CPUs of a task are online, it gets migrated to the fallback cpumask which is all the non nohz_full CPUs. However just like nohz_full CPUs, domain isolated CPUs don't want to be disturbed by tasks that have lost their CPU affinities. And since nohz_full rely on domain isolation to work correctly, the housekeeping mask of domain isolated CPUs should always be a superset of the housekeeping mask of nohz_full CPUs (there can be CPUs that are domain isolated but not nohz_full, OTOH there shouldn't be nohz_full CPUs that are not domain isolated): HK_TYPE_DOMAIN | HK_TYPE_KERNEL_NOISE == HK_TYPE_DOMAIN Therefore use HK_TYPE_DOMAIN as the appropriate fallback target for tasks and since this cpumask can be modified at runtime, make sure that 32 bits support CPUs on ARM64 mismatched systems are not isolated by cpusets. Signed-off-by: Frederic Weisbecker --- arch/arm64/kernel/cpufeature.c | 18 +++++++++++++++--- include/linux/cpu.h | 4 ++++ kernel/cgroup/cpuset.c | 17 ++++++++++++++--- 3 files changed, 33 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 5ed401ff79e3..4296b149ccf0 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1655,6 +1655,18 @@ has_cpuid_feature(const struct arm64_cpu_capabilities *entry, int scope) return feature_matches(val, entry); } +/* + * 32 bits support CPUs can't be isolated because tasks may be + * arbitrarily affine to them, defeating the purpose of isolation. + */ +bool arch_isolated_cpus_can_update(struct cpumask *new_cpus) +{ + if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) + return !cpumask_intersects(cpu_32bit_el0_mask, new_cpus); + else + return true; +} + const struct cpumask *system_32bit_el0_cpumask(void) { if (!system_supports_32bit_el0()) @@ -1668,7 +1680,7 @@ const struct cpumask *system_32bit_el0_cpumask(void) const struct cpumask *task_cpu_fallback_mask(struct task_struct *p) { - return __task_cpu_possible_mask(p, housekeeping_cpumask(HK_TYPE_TICK)); + return __task_cpu_possible_mask(p, housekeeping_cpumask(HK_TYPE_DOMAIN)); } static int __init parse_32bit_el0_param(char *str) @@ -3922,8 +3934,8 @@ static int enable_mismatched_32bit_el0(unsigned int cpu) bool cpu_32bit = false; if (id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0)) { - if (!housekeeping_cpu(cpu, HK_TYPE_TICK)) - pr_info("Treating adaptive-ticks CPU %u as 64-bit only\n", cpu); + if (!housekeeping_cpu(cpu, HK_TYPE_DOMAIN)) + pr_info("Treating domain isolated CPU %u as 64-bit only\n", cpu); else cpu_32bit = true; } diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 487b3bf2e1ea..0b48af25ab5c 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -229,4 +229,8 @@ static inline bool cpu_attack_vector_mitigated(enum cpu_attack_vectors v) #define smt_mitigations SMT_MITIGATIONS_OFF #endif +struct cpumask; + +bool arch_isolated_cpus_can_update(struct cpumask *new_cpus); + #endif /* _LINUX_CPU_H_ */ diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index d1a799e361c3..817c07a7a1b4 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1404,14 +1404,22 @@ static bool partition_xcpus_del(int old_prs, struct cpuset *parent, return isolcpus_updated; } +bool __weak arch_isolated_cpus_can_update(struct cpumask *new_cpus) +{ + return true; +} + /* - * isolated_cpus_can_update - check for isolated & nohz_full conflicts + * isolated_cpus_can_update - check for conflicts against housekeeping and + * CPUs capabilities. * @add_cpus: cpu mask for cpus that are going to be isolated * @del_cpus: cpu mask for cpus that are no longer isolated, can be NULL * Return: false if there is conflict, true otherwise * - * If nohz_full is enabled and we have isolated CPUs, their combination must - * still leave housekeeping CPUs. + * Check for conflicts: + * - If nohz_full is enabled and there are isolated CPUs, their combination must + * still leave housekeeping CPUs. + * - Architecture has CPU capabilities incompatible with being isolated */ static bool isolated_cpus_can_update(struct cpumask *add_cpus, struct cpumask *del_cpus) @@ -1419,6 +1427,9 @@ static bool isolated_cpus_can_update(struct cpumask *add_cpus, cpumask_var_t full_hk_cpus; int res = true; + if (!arch_isolated_cpus_can_update(add_cpus)) + return false; + if (!housekeeping_enabled(HK_TYPE_KERNEL_NOISE)) return true; -- 2.51.0