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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 F1F6EC4361B for ; Wed, 9 Dec 2020 04:11:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B19E0205ED for ; Wed, 9 Dec 2020 04:11:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727227AbgLIELL (ORCPT ); Tue, 8 Dec 2020 23:11:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:35228 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727168AbgLIELK (ORCPT ); Tue, 8 Dec 2020 23:11:10 -0500 X-Gm-Message-State: AOAM533usxQIqsp4Wd9eXSrnBw0uP7QnrAckgNoB4nvggk2AWEqG4P8j wreB1cop91KDvHBPjwR01fOTF5AZB2wJwpBJi3fxmA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1607487030; bh=1CAej7bL9bby2x2lbxE0YLEucpVIZk0Cp12eMTAWnCU=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=T/DygCw7+m4Ndk0b8X9tDQ1sje9jMArw8hFPLVfZvxK/6X/WoAzDv/Hc6oCC/69fZ 5JCSklUkI3lFSOrMehZ+rLBY/z4M8rtWz8s8IwGVWhOlVi+rci7YqYIscbDakpiwvy HQvraMymhvcL0NIpR6l6sL77A3NzQtdDuoTgbR3iwPp+KOKt4AwHWWIWVILOwbrf3p xjE4eUoQ8neBifqOxjQye9olx4DbQWzralHENI+EhuyU8dV4y0XhyIPhPGPReMExxo 3jnGPTjTlljwp3xDwX0LmfPqGolfuf3k0/mKxLNqcZDVdDyUZq8Yc7FXt8+Lh4xiFu 3qBciJaBGzzCA== X-Google-Smtp-Source: ABdhPJx8f+RdbaGI81UADW9xFSnrqCz4FjdPIOcomxSWAkAjhPQCAYJn9IG1EvCe9Bf6Ry8jGeQG8Y3nOpcc7KN9/Lc= X-Received: by 2002:a1c:630b:: with SMTP id x11mr567584wmb.138.1607487028407; Tue, 08 Dec 2020 20:10:28 -0800 (PST) MIME-Version: 1.0 References: <5afc7632be1422f91eaf7611aaaa1b5b8580a086.1607058304.git.luto@kernel.org> In-Reply-To: <5afc7632be1422f91eaf7611aaaa1b5b8580a086.1607058304.git.luto@kernel.org> From: Andy Lutomirski Date: Tue, 8 Dec 2020 20:10:17 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 1/4] x86/membarrier: Get rid of a dubious optimization To: Andy Lutomirski Cc: X86 ML , Mathieu Desnoyers , LKML , Nicholas Piggin , Arnd Bergmann , Anton Blanchard , stable Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 3, 2020 at 9:07 PM Andy Lutomirski wrote: > > sync_core_before_usermode() had an incorrect optimization. If we're > in an IRQ, we can get to usermode without IRET -- we just have to > schedule to a different task in the same mm and do SYSRET. > Fortunately, there were no callers of sync_core_before_usermode() > that could have had in_irq() or in_nmi() equal to true, because it's > only ever called from the scheduler. > > While we're at it, clarify a related comment. > Fixes: ac1ab12a3e6e ("lockin/x86: Implement sync_core_before_usermode()") > Cc: stable@vger.kernel.org > Reviewed-by: Mathieu Desnoyers > Signed-off-by: Andy Lutomirski