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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29A63C433F5 for ; Mon, 3 Oct 2022 23:18:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229754AbiJCXR7 (ORCPT ); Mon, 3 Oct 2022 19:17:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41958 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229571AbiJCXR4 (ORCPT ); Mon, 3 Oct 2022 19:17:56 -0400 Received: from mail-pg1-x531.google.com (mail-pg1-x531.google.com [IPv6:2607:f8b0:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C438BDD2; Mon, 3 Oct 2022 16:17:55 -0700 (PDT) Received: by mail-pg1-x531.google.com with SMTP id a23so3290651pgi.10; Mon, 03 Oct 2022 16:17:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=to:references:message-id:content-transfer-encoding:cc:date :in-reply-to:from:subject:mime-version:from:to:cc:subject:date; bh=cF6w9w5X7amibS6REZNPvQpkz6hVdgXqlpPTRgjKOOU=; b=EdhdDGXccvWvAcdeD8lKaCH9Qlu8RC1doJmdQv10fYLzDxDnFHinxgTu7ZVp3hSxnx 2dfOgLm/ifEfE7tWxOlAl5GKBKeSKuZYvVc0MpBJhfSzkBDd0GG5yWXzPHFIoe7Acnvt 7ffe9OYuua1fSTX7G+l97pE2EqOcGDcxfn2KQYiOKfrSwJJhnHYBBJuHHie335oLn9Bt m+YUFW7HRp/FgJISMk4C0UQUCSOq2do0gLRgqQnOHO6z7b6J+zwizQJXckKIiLwzwJ3w UWAG3ka0c3bn9FIFyYNJvkAr6T2/b99u3MwyQy9UlPFZ7rWJKQ2335FNc8tZb0UZ2jLD i5Bw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=to:references:message-id:content-transfer-encoding:cc:date :in-reply-to:from:subject:mime-version:x-gm-message-state:from:to:cc :subject:date; bh=cF6w9w5X7amibS6REZNPvQpkz6hVdgXqlpPTRgjKOOU=; b=uH8c6Cq/ZPtzkaPcSrPWJc3FBHRh5nzvNAhYRhX1TmzMsNT1H/tB7bM1AGm4X1kDOB VH55XoX8eIB8RW83ME9e68YxFfwMPuwgrEUvy8tN0E4y7ZLmBHz2+BhALvHUDz5QYcE6 h8wJKTRxjykGYNn7tuT1U1ke18TeMn+LypOocCapg5hEQVcCTsrhCDiEjBnJVW9tXbP4 41qO5kC9XOLv27gERSotmf7/CF0mNyzwKGwnpzJ45K7rp5xRkeo+i7aOagbZURa7xFqh ZPPNja0xQs9IkcCWHJU+m/yu3mwHWm3tKuFQMH3dfkXOtGNJ2m2YAzkUC58bmOO9jNyW WCqw== X-Gm-Message-State: ACrzQf22bkLGCK+DsKZgLoXER2DpQGRBZ3+joioUgpFK0NHpeSoEzdl0 L+nfgY8MA2yPsCOAsCT+oCo= X-Google-Smtp-Source: AMsMyM4n/AJvFE/d3TYFJJYJ4un/v9u7OCLnjbu3wozi/xsNx3IhRWyZCu0U8G5vBhH2rNE3kNGwNQ== X-Received: by 2002:a62:8342:0:b0:560:fea3:f45e with SMTP id h63-20020a628342000000b00560fea3f45emr9606455pfe.45.1664839075037; Mon, 03 Oct 2022 16:17:55 -0700 (PDT) Received: from smtpclient.apple ([66.170.99.2]) by smtp.gmail.com with ESMTPSA id l16-20020a170902f69000b0016c5306917fsm7825144plg.53.2022.10.03.16.17.52 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 03 Oct 2022 16:17:54 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.1\)) Subject: Re: [PATCH v2 12/39] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW From: Nadav Amit In-Reply-To: <64313344833c3b1701002a347d539e69276b66fb.camel@intel.com> Date: Mon, 3 Oct 2022 16:17:51 -0700 Cc: "bsingharora@gmail.com" , "hpa@zytor.com" , "Syromiatnikov, Eugene" , "peterz@infradead.org" , "rdunlap@infradead.org" , "keescook@chromium.org" , "Yu, Yu-cheng" , "dave.hansen@linux.intel.com" , "kirill.shutemov@linux.intel.com" , "Eranian, Stephane" , "linux-mm@kvack.org" , "fweimer@redhat.com" , "jannh@google.com" , "dethoma@microsoft.com" , "linux-arch@vger.kernel.org" , "kcc@google.com" , "bp@alien8.de" , "oleg@redhat.com" , "hjl.tools@gmail.com" , "Yang, Weijiang" , Andy Lutomirski , "pavel@ucw.cz" , "arnd@arndb.de" , "Moreira, Joao" , Thomas Gleixner , "mike.kravetz@oracle.com" , "x86@kernel.org" , "linux-doc@vger.kernel.org" , "jamorris@linux.microsoft.com" , "john.allen@amd.com" , "rppt@kernel.org" , "mingo@redhat.com" , "Shankar, Ravi V" , "corbet@lwn.net" , "linux-kernel@vger.kernel.org" , "linux-api@vger.kernel.org" , "gorcunov@gmail.com" Content-Transfer-Encoding: quoted-printable Message-Id: <35EEB9F0-D99A-4664-9628-27029B52CFD1@gmail.com> References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-13-rick.p.edgecombe@intel.com> <64313344833c3b1701002a347d539e69276b66fb.camel@intel.com> To: "Edgecombe, Rick P" X-Mailer: Apple Mail (2.3696.120.41.1.1) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Oct 3, 2022, at 3:28 PM, Edgecombe, Rick P = wrote: > On Mon, 2022-10-03 at 11:11 -0700, Nadav Amit wrote: >> Did you have a look at ptep_set_access_flags() and friends and >> checked they >> do not need to be changed too?=20 >=20 > ptep_set_access_flags() doesn't actually set any additional dirty bits > on x86, so I think it's ok. Are you sure about that? (lost my confidence today so I am hesitant). Looking on insert_pfn(), I see: entry =3D maybe_mkwrite(pte_mkdirty(entry), = vma); if (ptep_set_access_flags(vma, addr, pte, entry, = 1)) ... This appears to set the dirty bit while potentially leaving the = write-bit clear. This is the scenario you want to avoid, no? >> Perhaps you should at least add some >> assertion just to ensure nothing breaks. >=20 > You mean in ptep_set_access_flags()? I think some assertions would be > really great, I'm just not sure where. Yes, on x86=E2=80=99s version of the function.