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 X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83A8FC56201 for ; Mon, 23 Nov 2020 02:25:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3F8FE208B8 for ; Mon, 23 Nov 2020 02:25:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727028AbgKWCY7 (ORCPT ); Sun, 22 Nov 2020 21:24:59 -0500 Received: from foss.arm.com ([217.140.110.172]:51754 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726885AbgKWCY7 (ORCPT ); Sun, 22 Nov 2020 21:24:59 -0500 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 CDFD9113E; Sun, 22 Nov 2020 18:24:58 -0800 (PST) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 7A8A33F70D; Sun, 22 Nov 2020 18:24:57 -0800 (PST) From: Valentin Schneider To: linux-kernel@vger.kernel.org, x86@kernel.org Cc: James Morse , Fenghua Yu , Reinette Chatre , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" Subject: [PATCH v2 3/3] x86/intel_rdt: Apply READ_ONCE/WRITE_ONCE to task_struct .rmid & .closid Date: Mon, 23 Nov 2020 02:24:33 +0000 Message-Id: <20201123022433.17905-4-valentin.schneider@arm.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20201123022433.17905-1-valentin.schneider@arm.com> References: <20201123022433.17905-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A CPU's current task can have its {closid, rmid} fields read locally while they are being concurrently written to from another CPU. This can happen anytime __resctrl_sched_in() races with e.g. a __rdtgroup_move_task() call on a different CPU targeting the first CPU's current task. Prevent load / store tearing for those accesses by giving them the READ_ONCE() / WRITE_ONCE() treatment. Reviewed-by: James Morse Signed-off-by: Valentin Schneider --- arch/x86/include/asm/resctrl.h | 11 +++++++---- arch/x86/kernel/cpu/resctrl/rdtgroup.c | 24 +++++++++++++----------- 2 files changed, 20 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h index 07603064df8f..d60ed0668a59 100644 --- a/arch/x86/include/asm/resctrl.h +++ b/arch/x86/include/asm/resctrl.h @@ -56,19 +56,22 @@ static void __resctrl_sched_in(void) struct resctrl_pqr_state *state = this_cpu_ptr(&pqr_state); u32 closid = state->default_closid; u32 rmid = state->default_rmid; + u32 tmp; /* * If this task has a closid/rmid assigned, use it. * Else use the closid/rmid assigned to this cpu. */ if (static_branch_likely(&rdt_alloc_enable_key)) { - if (current->closid) - closid = current->closid; + tmp = READ_ONCE(current->closid); + if (tmp) + closid = tmp; } if (static_branch_likely(&rdt_mon_enable_key)) { - if (current->rmid) - rmid = current->rmid; + tmp = READ_ONCE(current->rmid); + if (tmp) + rmid = tmp; } if (closid != state->cur_closid || rmid != state->cur_rmid) { diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c index f62d81104fd0..135a51529f70 100644 --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c @@ -529,8 +529,8 @@ static void move_myself(struct callback_head *head) */ if (atomic_dec_and_test(&rdtgrp->waitcount) && (rdtgrp->flags & RDT_DELETED)) { - current->closid = 0; - current->rmid = 0; + WRITE_ONCE(current->closid, 0); + WRITE_ONCE(current->rmid, 0); kfree(rdtgrp); } @@ -565,8 +565,8 @@ static int __rdtgroup_move_task(struct task_struct *tsk, * their parent CTRL group. */ if (rdtgrp->type == RDTCTRL_GROUP) - tsk->closid = rdtgrp->closid; - tsk->rmid = rdtgrp->mon.rmid; + WRITE_ONCE(tsk->closid, rdtgrp->closid); + WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid); /* * Take a refcount, so rdtgrp cannot be freed before the @@ -598,13 +598,15 @@ static int __rdtgroup_move_task(struct task_struct *tsk, static bool is_closid_match(struct task_struct *t, struct rdtgroup *r) { return (rdt_alloc_capable && - (r->type == RDTCTRL_GROUP) && (t->closid == r->closid)); + (r->type == RDTCTRL_GROUP) && + (READ_ONCE(t->closid) == r->closid)); } static bool is_rmid_match(struct task_struct *t, struct rdtgroup *r) { return (rdt_mon_capable && - (r->type == RDTMON_GROUP) && (t->rmid == r->mon.rmid)); + (r->type == RDTMON_GROUP) && + (READ_ONCE(t->rmid) == r->mon.rmid)); } /** @@ -680,7 +682,7 @@ static int rdtgroup_move_task(pid_t pid, struct rdtgroup *rdtgrp, goto out; if (rdtgrp->type == RDTMON_GROUP && - rdtgrp->mon.parent->closid != tsk->closid) { + rdtgrp->mon.parent->closid != READ_ONCE(tsk->closid)) { rdt_last_cmd_puts("Can't move task to different control group\n"); ret = -EINVAL; goto out; @@ -810,7 +812,7 @@ int proc_resctrl_show(struct seq_file *s, struct pid_namespace *ns, rdtg->mode != RDT_MODE_EXCLUSIVE) continue; - if (rdtg->closid != tsk->closid) + if (rdtg->closid != READ_ONCE(tsk->closid)) continue; seq_printf(s, "res:%s%s\n", (rdtg == &rdtgroup_default) ? "/" : "", @@ -818,7 +820,7 @@ int proc_resctrl_show(struct seq_file *s, struct pid_namespace *ns, seq_puts(s, "mon:"); list_for_each_entry(crg, &rdtg->mon.crdtgrp_list, mon.crdtgrp_list) { - if (tsk->rmid != crg->mon.rmid) + if (READ_ONCE(tsk->rmid) != crg->mon.rmid) continue; seq_printf(s, "%s", crg->kn->name); break; @@ -2336,8 +2338,8 @@ static void rdt_move_group_tasks(struct rdtgroup *from, struct rdtgroup *to, for_each_process_thread(p, t) { if (!from || is_closid_match(t, from) || is_rmid_match(t, from)) { - t->closid = to->closid; - t->rmid = to->mon.rmid; + WRITE_ONCE(t->closid, to->closid); + WRITE_ONCE(t->rmid, to->mon.rmid); #ifdef CONFIG_SMP /* -- 2.27.0