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[2620:137:e000::1:20]) by mx.google.com with ESMTP id f12-20020a17090a654c00b00250ab2f31besi2050972pjs.71.2023.05.25.11.05.15; Thu, 25 May 2023 11:05:29 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241160AbjEYSDt (ORCPT + 99 others); Thu, 25 May 2023 14:03:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33046 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241046AbjEYSD0 (ORCPT ); Thu, 25 May 2023 14:03:26 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 6B2F619D for ; Thu, 25 May 2023 11:03:06 -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 316781655; Thu, 25 May 2023 11:03:51 -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 65FF83F6C4; Thu, 25 May 2023 11:03:03 -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, xingxin.hx@openanolis.org, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com Subject: [PATCH v4 12/24] x86/resctrl: Make resctrl_arch_rmid_read() retry when it is interrupted Date: Thu, 25 May 2023 18:01:57 +0000 Message-Id: <20230525180209.19497-13-james.morse@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20230525180209.19497-1-james.morse@arm.com> References: <20230525180209.19497-1-james.morse@arm.com> MIME-Version: 1.0 X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1766890331613325230?= X-GMAIL-MSGID: =?utf-8?q?1766890331613325230?= resctrl_arch_rmid_read() could be called by resctrl in process context, and then called by the PMU driver from irq context on the same CPU. This could cause struct arch_mbm_state's prev_msr value to go backwards, leading to the chunks value being incremented multiple times. The struct arch_mbm_state holds both the previous msr value, and a count of the number of chunks. These two fields need to be updated atomically. Read the prev_msr before accessing the hardware, and cmpxchg() the value back. If the value has changed, the whole thing is re-attempted. Signed-off-by: James Morse --- arch/x86/kernel/cpu/resctrl/internal.h | 5 +++-- arch/x86/kernel/cpu/resctrl/monitor.c | 28 +++++++++++++++++++------- 2 files changed, 24 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h index 6f18cf26988c..7960366b9434 100644 --- a/arch/x86/kernel/cpu/resctrl/internal.h +++ b/arch/x86/kernel/cpu/resctrl/internal.h @@ -2,6 +2,7 @@ #ifndef _ASM_X86_RESCTRL_INTERNAL_H #define _ASM_X86_RESCTRL_INTERNAL_H +#include #include #include #include @@ -338,8 +339,8 @@ struct mbm_state { * find this struct. */ struct arch_mbm_state { - u64 chunks; - u64 prev_msr; + atomic64_t chunks; + atomic64_t prev_msr; }; /** diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c index e267869d60d5..1f470e55d555 100644 --- a/arch/x86/kernel/cpu/resctrl/monitor.c +++ b/arch/x86/kernel/cpu/resctrl/monitor.c @@ -225,13 +225,15 @@ void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_domain *d, { struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d); struct arch_mbm_state *am; + u64 msr_val; am = get_arch_mbm_state(hw_dom, rmid, eventid); if (am) { memset(am, 0, sizeof(*am)); /* Record any initial, non-zero count value. */ - __rmid_read(rmid, eventid, &am->prev_msr); + __rmid_read(rmid, eventid, &msr_val); + atomic64_set(&am->prev_msr, msr_val); } } @@ -266,23 +268,35 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d, { struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r); struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d); + u64 start_msr_val, old_msr_val, msr_val, chunks; struct arch_mbm_state *am; - u64 msr_val, chunks; - int ret; + int ret = 0; if (!cpumask_test_cpu(smp_processor_id(), &d->cpu_mask)) return -EINVAL; +interrupted: + am = get_arch_mbm_state(hw_dom, rmid, eventid); + if (am) + start_msr_val = atomic64_read(&am->prev_msr); + ret = __rmid_read(rmid, eventid, &msr_val); if (ret) return ret; am = get_arch_mbm_state(hw_dom, rmid, eventid); if (am) { - am->chunks += mbm_overflow_count(am->prev_msr, msr_val, - hw_res->mbm_width); - chunks = get_corrected_mbm_count(rmid, am->chunks); - am->prev_msr = msr_val; + old_msr_val = atomic64_cmpxchg(&am->prev_msr, start_msr_val, + msr_val); + if (old_msr_val != start_msr_val) + goto interrupted; + + chunks = mbm_overflow_count(start_msr_val, msr_val, + hw_res->mbm_width); + atomic64_add(chunks, &am->chunks); + + chunks = get_corrected_mbm_count(rmid, + atomic64_read(&am->chunks)); } else { chunks = msr_val; }