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 BACEAC43461 for ; Tue, 13 Apr 2021 16:23:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9DEED61369 for ; Tue, 13 Apr 2021 16:23:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343957AbhDMQYO (ORCPT ); Tue, 13 Apr 2021 12:24:14 -0400 Received: from mail-pg1-f180.google.com ([209.85.215.180]:42588 "EHLO mail-pg1-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245265AbhDMQYF (ORCPT ); Tue, 13 Apr 2021 12:24:05 -0400 Received: by mail-pg1-f180.google.com with SMTP id g35so12270524pgg.9 for ; Tue, 13 Apr 2021 09:23:46 -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=myAv69MaFRKWn2I2SW1R2lECVQNHL7kM1EUxjGkHBlQ=; b=oGJsz6THEkUmu6g0msyh2jGLGrJu8yfMEfsQK09Pcppqy1roF2NR0hk5Lb/mnInxkM Mb9bvlJoqJ9fJ9aekXnq0qAE9jcQVe8f+FqaJjr3rJugVJIiKy+E4jt6+VThoSmbvQbb 7L31Bbfce313S9AaK1/uiTtDi01lNrXXSLuRSpblDTihdTBeIVvAyV1V19U46Q/7AZf5 q9TbnDFYuTmJpx5k9zRyvsUojW1pPBRhy2+ilZErVt64qmYyjWd4NEdX531aWLtNTK4+ ovuObeCfVBPiP6dxx38R+G5MseGGiWNuvLQcKhmnXowOXh7M9AeKw80E99QNmmK1GyCt EQ2Q== 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=myAv69MaFRKWn2I2SW1R2lECVQNHL7kM1EUxjGkHBlQ=; b=uYUuVLkPES18jHnIwOsxLrDUWmYLfezrCK25oI2kOiHSlfu0guCZQEjAk5urSTvS/l Tc+J3tK9uGk5sU6JqotjwAJoUDR3YlB3yarOylUO11TguHCto1sBLQRDsuJwkv6UNRnk xhSBLfvV76xWf/XtDEUlDinlN5FMpRedDyXyc56Ad8tbtiy1K3AX3HsXyLDGuTHXpCmu XNLZbc3YjBopn+6etFjgBHCHoa2v0lz021KxKiGHqsljctNLZIbRFBUw0rfQIG5dXRzo R2UvJVRPADB2Y/YFAZNklOciDlH5bE5cZ1dHG2KprlOhayreAW0W6NXO/U9rHhGoy00X Lang== X-Gm-Message-State: AOAM532bp/hbrLuEJ7UXiUSknOgLsIu5i8LIYCMS21WwH2sKo8sOD+w3 N/mPPwXdMD4JOHSav/d7EMQ= X-Google-Smtp-Source: ABdhPJwQi9mr5U6edH0lo57bbRVeP6zWUW8Dx5z496iCDv2DmUIXXoUrNrWjTTeU13+CMVszBc/pug== X-Received: by 2002:a63:4c4:: with SMTP id 187mr33036304pge.187.1618330966051; Tue, 13 Apr 2021 09:22:46 -0700 (PDT) Received: from edumazet1.svl.corp.google.com ([2620:15c:2c4:201:485b:46b2:8be1:2cdd]) by smtp.gmail.com with ESMTPSA id l25sm15897591pgu.72.2021.04.13.09.22.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Apr 2021 09:22:45 -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 v2 1/3] rseq: optimize rseq_update_cpu_id() Date: Tue, 13 Apr 2021 09:22:37 -0700 Message-Id: <20210413162240.3131033-2-eric.dumazet@gmail.com> X-Mailer: git-send-email 2.31.1.295.g9ea45b61b8-goog In-Reply-To: <20210413162240.3131033-1-eric.dumazet@gmail.com> References: <20210413162240.3131033-1-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..f020f18f512a3f6241c3c9b104ce50e4d2c6188c 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 __user *rseq = 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(rseq, sizeof(*rseq))) + goto efault; + unsafe_put_user(cpu_id, &rseq->cpu_id_start, efault_end); + unsafe_put_user(cpu_id, &rseq->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