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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 B042BC433ED for ; Tue, 13 Apr 2021 07:37:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7F30E6135C for ; Tue, 13 Apr 2021 07:37:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241760AbhDMHhj (ORCPT ); Tue, 13 Apr 2021 03:37:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237883AbhDMHhY (ORCPT ); Tue, 13 Apr 2021 03:37:24 -0400 Received: from mail-pl1-x62a.google.com (mail-pl1-x62a.google.com [IPv6:2607:f8b0:4864:20::62a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C78EC061574 for ; Tue, 13 Apr 2021 00:37:05 -0700 (PDT) Received: by mail-pl1-x62a.google.com with SMTP id d8so7734713plh.11 for ; Tue, 13 Apr 2021 00:37:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=lY+BvEE2MyA/W5iizb1+I2X/2gi/Ot/SaAWBNm40SKc=; b=N0z3JMwCZbLees7ZXAFo7xVyRVS64HlYoJWOAsfnRZjmpbKbtYBJr4DI9Xzy7Wy+x6 0yTXADLiq9TNzEGwB/mvbNzIDaWzhqI3x/905Czr9QFM+pvNCtK9ZhIpOamIgAhxuYF3 OXeSRsDw3i82Nm2sjWMytuseaguv9FYhPQZsNSw8aMBVS7kwwg+qsULjzQVkeDDX8Fvt fQLNgIHMfhftQkQfvBcFYNaEriQjHBbT6JU5Nd1wv8B2wZ35wwHfPMr8YqUjv43MPhh/ 0T/AAUunGnEZ7ZWBQr25ekw1OySeo3X+UMKiFS2pyUs9tz/DIGk7/QPvRjEdP1R81wOD s6Bg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=lY+BvEE2MyA/W5iizb1+I2X/2gi/Ot/SaAWBNm40SKc=; b=bG/X3QSS1GUTPPBrNbPgLaTVXs/YKyYo/wpiLPNdIaBSVJG4Y3vPGR+8gK/LoKhdfN EsDq3xket/k5MSsNNrlsHjK5lXoNWgjJQwYigLXGrxX47EC+4311R/9rYDWg1hW0zNRF jhcrCK0cv61JFGEr2W88zupd8bxPQafd78yt9AUavuDSWutcTCizsx71/xdfMsgGlEwN i3/MXR4LzDEeYnOQbqZcmxBAXAB3Z+GEitLF/wKh6DKbU+/ytHJ/pkn34aL4k6wbB9mb 3KSDhyluQwtx6RZGqSjOL7lKcf6TI5KMlCgwHxQ7JhuuwlwWZvmLCCiPRUhJattYyJ5Y Gh4A== X-Gm-Message-State: AOAM5305psk+czrC1A3HGuZ+RZKDLzypFf7Ya/EfKn2limme/8yKFaEC Zu/t7en/saQDdJC9micwLF8= X-Google-Smtp-Source: ABdhPJwHz8U4+7dZPA7iaT7pzX9Y8YSyn9ndZQmoXZmm0483t141RWtKUbsN1wyiP76VAP7foWd/EA== X-Received: by 2002:a17:902:d104:b029:eb:6d3:1436 with SMTP id w4-20020a170902d104b02900eb06d31436mr7559974plw.1.1618299425013; Tue, 13 Apr 2021 00:37:05 -0700 (PDT) Received: from edumazet1.svl.corp.google.com ([2620:15c:2c4:201:71d7:d843:bfe8:bec7]) by smtp.gmail.com with ESMTPSA id a3sm1349068pjq.36.2021.04.13.00.37.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Apr 2021 00:37:04 -0700 (PDT) From: Eric Dumazet To: Ingo Molnar , Mathieu Desnoyers , Peter Zijlstra Cc: "Paul E . McKenney" , Boqun Feng , Arjun Roy , linux-kernel , Eric Dumazet , Eric Dumazet Subject: [PATCH 1/3] rseq: optimize rseq_update_cpu_id() Date: Tue, 13 Apr 2021 00:36:55 -0700 Message-Id: <20210413073657.2308450-2-eric.dumazet@gmail.com> X-Mailer: git-send-email 2.31.1.295.g9ea45b61b8-goog In-Reply-To: <20210413073657.2308450-1-eric.dumazet@gmail.com> References: <20210413073657.2308450-1-eric.dumazet@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet Two put_user() in rseq_update_cpu_id() are replaced by a pair of unsafe_put_user() with appropriate surroundings. This removes one stac/clac pair on x86 in fast path. Signed-off-by: Eric Dumazet Cc: Mathieu Desnoyers Cc: Peter Zijlstra Cc: "Paul E. McKenney" Cc: Boqun Feng Cc: Arjun Roy Cc: Ingo Molnar --- kernel/rseq.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/kernel/rseq.c b/kernel/rseq.c index a4f86a9d6937cdfa2f13d1dcc9be863c1943d06f..d2689ccbb132c0fc8ec0924008771e5ee1ca855e 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -84,13 +84,20 @@ static int rseq_update_cpu_id(struct task_struct *t) { u32 cpu_id = raw_smp_processor_id(); + struct rseq *r = t->rseq; - if (put_user(cpu_id, &t->rseq->cpu_id_start)) - return -EFAULT; - if (put_user(cpu_id, &t->rseq->cpu_id)) - return -EFAULT; + if (!user_write_access_begin(r, sizeof(*r))) + goto efault; + unsafe_put_user(cpu_id, &r->cpu_id_start, efault_end); + unsafe_put_user(cpu_id, &r->cpu_id, efault_end); + user_write_access_end(); trace_rseq_update(t); return 0; + +efault_end: + user_write_access_end(); +efault: + return -EFAULT; } static int rseq_reset_rseq_cpu_id(struct task_struct *t) -- 2.31.1.295.g9ea45b61b8-goog