From nobody Wed Dec 17 12:55:23 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C593C07545 for ; Wed, 25 Oct 2023 18:06:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234945AbjJYSGb (ORCPT ); Wed, 25 Oct 2023 14:06:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234936AbjJYSF4 (ORCPT ); Wed, 25 Oct 2023 14:05:56 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C51D819B for ; Wed, 25 Oct 2023 11:05:40 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 090C41515; Wed, 25 Oct 2023 11:06:22 -0700 (PDT) Received: from merodach.members.linode.com (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 41F5F3F738; Wed, 25 Oct 2023 11:05:37 -0700 (PDT) From: James Morse To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Fenghua Yu , Reinette Chatre , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Babu Moger , James Morse , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com Subject: [PATCH v7 16/24] x86/resctrl: Make resctrl_mounted checks explicit Date: Wed, 25 Oct 2023 18:03:37 +0000 Message-Id: <20231025180345.28061-17-james.morse@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20231025180345.28061-1-james.morse@arm.com> References: <20231025180345.28061-1-james.morse@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The rdt_enable_key is switched when resctrl is mounted, and used to prevent a second mount of the filesystem. It also enables the architecture's context switch code. This requires another architecture to have the same set of static-keys, as resctrl depends on them too. The existing users of these static-keys are implicitly also checking if the filesystem is mounted. Make the resctrl_mounted checks explicit: resctrl can keep track of whether it has been mounted once. This doesn't need to be combined with whether the arch code is context switching the CLOSID. rdt_mon_enable_key is never used just to test that resctrl is mounted, but does also have this implication. Add a resctrl_mounted to all uses of rdt_mon_enable_key. This will allow rdt_mon_enable_key to be swapped with a helper in a subsequent patch. This will allow the static-key changing to be moved behind resctrl_arch_ calls. Tested-by: Shaopeng Tan Tested-by: Peter Newman Reviewed-by: Shaopeng Tan Reviewed-by: Reinette Chatre Signed-off-by: James Morse Reviewed-by: Babu Moger --- Changes since v3: * Removed a newline. * Rephrased commit message Changes since v4: * Rephrased comment. No changes since v6 --- arch/x86/kernel/cpu/resctrl/internal.h | 1 + arch/x86/kernel/cpu/resctrl/monitor.c | 12 ++++++++++-- arch/x86/kernel/cpu/resctrl/rdtgroup.c | 23 +++++++++++++++++------ 3 files changed, 28 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/r= esctrl/internal.h index bb07b9b01e36..5ce49503fcd8 100644 --- a/arch/x86/kernel/cpu/resctrl/internal.h +++ b/arch/x86/kernel/cpu/resctrl/internal.h @@ -145,6 +145,7 @@ extern bool rdt_alloc_capable; extern bool rdt_mon_capable; extern unsigned int rdt_mon_features; extern struct list_head resctrl_schema_all; +extern bool resctrl_mounted; =20 enum rdt_group_type { RDTCTRL_GROUP =3D 0, diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/re= sctrl/monitor.c index 1ca8db8c82cc..843df6f64e0e 100644 --- a/arch/x86/kernel/cpu/resctrl/monitor.c +++ b/arch/x86/kernel/cpu/resctrl/monitor.c @@ -837,7 +837,11 @@ void mbm_handle_overflow(struct work_struct *work) =20 mutex_lock(&rdtgroup_mutex); =20 - if (!static_branch_likely(&rdt_mon_enable_key)) + /* + * If the filesystem has been unmounted this work no longer needs to + * run. + */ + if (!resctrl_mounted || !static_branch_likely(&rdt_mon_enable_key)) goto out_unlock; =20 r =3D &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl; @@ -870,7 +874,11 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom= , unsigned long delay_ms) unsigned long delay =3D msecs_to_jiffies(delay_ms); int cpu; =20 - if (!static_branch_likely(&rdt_mon_enable_key)) + /* + * When a domain comes online there is no guarantee the filesystem is + * mounted. If not, there is no need to catch counter overflow. + */ + if (!resctrl_mounted || !static_branch_likely(&rdt_mon_enable_key)) return; cpu =3D cpumask_any_housekeeping(&dom->cpu_mask); dom->mbm_work_cpu =3D cpu; diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/r= esctrl/rdtgroup.c index fe6dfea471f2..9ce1f981c8e1 100644 --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c @@ -42,6 +42,9 @@ LIST_HEAD(rdt_all_groups); /* list of entries for the schemata file */ LIST_HEAD(resctrl_schema_all); =20 +/* The filesystem can only be mounted once. */ +bool resctrl_mounted; + /* Kernel fs node for "info" directory under root */ static struct kernfs_node *kn_info; =20 @@ -881,7 +884,7 @@ int proc_resctrl_show(struct seq_file *s, struct pid_na= mespace *ns, mutex_lock(&rdtgroup_mutex); =20 /* Return empty if resctrl has not been mounted. */ - if (!static_branch_unlikely(&rdt_enable_key)) { + if (!resctrl_mounted) { seq_puts(s, "res:\nmon:\n"); goto unlock; } @@ -2613,7 +2616,7 @@ static int rdt_get_tree(struct fs_context *fc) /* * resctrl file system can only be mounted once. */ - if (static_branch_unlikely(&rdt_enable_key)) { + if (resctrl_mounted) { ret =3D -EBUSY; goto out; } @@ -2674,8 +2677,10 @@ static int rdt_get_tree(struct fs_context *fc) if (rdt_mon_capable) static_branch_enable_cpuslocked(&rdt_mon_enable_key); =20 - if (rdt_alloc_capable || rdt_mon_capable) + if (rdt_alloc_capable || rdt_mon_capable) { static_branch_enable_cpuslocked(&rdt_enable_key); + resctrl_mounted =3D true; + } =20 if (is_mbm_enabled()) { r =3D &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl; @@ -2949,6 +2954,7 @@ static void rdt_kill_sb(struct super_block *sb) static_branch_disable_cpuslocked(&rdt_alloc_enable_key); static_branch_disable_cpuslocked(&rdt_mon_enable_key); static_branch_disable_cpuslocked(&rdt_enable_key); + resctrl_mounted =3D false; kernfs_kill_sb(sb); mutex_unlock(&rdtgroup_mutex); cpus_read_unlock(); @@ -3918,7 +3924,7 @@ void resctrl_offline_domain(struct rdt_resource *r, s= truct rdt_domain *d) * If resctrl is mounted, remove all the * per domain monitor data directories. */ - if (static_branch_unlikely(&rdt_mon_enable_key)) + if (resctrl_mounted && static_branch_unlikely(&rdt_mon_enable_key)) rmdir_mondata_subdir_allrdtgrp(r, d->id); =20 if (is_mbm_enabled()) @@ -3995,8 +4001,13 @@ int resctrl_online_domain(struct rdt_resource *r, st= ruct rdt_domain *d) if (is_llc_occupancy_enabled()) INIT_DELAYED_WORK(&d->cqm_limbo, cqm_handle_limbo); =20 - /* If resctrl is mounted, add per domain monitor data directories. */ - if (static_branch_unlikely(&rdt_mon_enable_key)) + /* + * If the filesystem is not mounted then only the default resource group + * exists. Creation of its directories is deferred until mount time + * by rdt_get_tree() calling mkdir_mondata_all(). + * If resctrl is mounted, add per domain monitor data directories. + */ + if (resctrl_mounted && static_branch_unlikely(&rdt_mon_enable_key)) mkdir_mondata_subdir_allrdtgrp(r, d); =20 return 0; --=20 2.39.2