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 164E5C4332F for ; Fri, 30 Sep 2022 15:17:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231879AbiI3PRJ (ORCPT ); Fri, 30 Sep 2022 11:17:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60472 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231726AbiI3PQ5 (ORCPT ); Fri, 30 Sep 2022 11:16:57 -0400 Received: from mail-io1-xd30.google.com (mail-io1-xd30.google.com [IPv6:2607:f8b0:4864:20::d30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 57D8E156571 for ; Fri, 30 Sep 2022 08:16:50 -0700 (PDT) Received: by mail-io1-xd30.google.com with SMTP id p202so3507745iod.6 for ; Fri, 30 Sep 2022 08:16:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=rav/GnxDxXCmb0MWmQJI5rI/wm0ZOCSwNoHHz9z+r7A=; b=YB6CjrLNYng7WeQ+wslm2VPbitaNP0ShR1T5EE1nM1ZDzkPIUIob+C5C13QD3JXPF1 NlTKpUe1scku9p9XtGg1Izf8Dc1TpUfDODtn3jM3q+jUgY+zDC8CkVafqeyuUs5Ukq4H mxgGAAK+DsgqM6tuU2p8NgFuDB9wt0vJRVLYwkBPKv4B/ePv4XSF+IhrLjGkmdoqQgiK rxRERHXXtZc2phGR1txS5Ern3RsbTR4MwgYbmiOu6gqswdwU6HISzy3r1yVdTddsuKrM iiaVoLmXP/g0d+Kep6mJQOi0gGm+i42CSw87iKLR+VGAZR0m1PHT3JTUY1Mdx8cOHtjv UphQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=rav/GnxDxXCmb0MWmQJI5rI/wm0ZOCSwNoHHz9z+r7A=; b=wO1zjz9cEpVd1TW3/UaxpuPyWzocwmf+YBuUzcZwwE+6bUCZWvgzcPNimDmIHXXJkw k/Z8/hyiG7sVvp7Gn2c9oE/k6z0kkPlZp6KMM+FmuTs5UuyjAsKHlvwt77e0Rz0ptJad cLP6pry6tGTsRAu9pr6tqLmf3muYFygWmWMoDpWDhczBCcYW5jt3qSJrscBYpPxEzqOX lvCBskYaLgSXWRBsQSzVVUpSY63IwFWGDDV7Kdmm1T9S19EwPJBvR0c1H6HWa5j5zf1J NXX2VkpcU98D7tdBDGqPJBiJ+PggLE7a85mSs2vFwYGfWiU8U/SvD33sbHtqorsauM7g XXVA== X-Gm-Message-State: ACrzQf1pOUw2EDJffrcmREUahMx0oDVRBgQd+nNHWRbVaVlZyF5wPYqt SqIw+7j3hnUZI1PP5gZR9/vTNVSH2F7oaJrAJnQc2w== X-Google-Smtp-Source: AMsMyM6F7AAgEnbDB3rrGofw7Np/IRuyPPKXtazfBLnfUtfrHBecx6ZQ4/DCYfPtN9Dyv/lb8mRBcckQ17dphsFV0xw= X-Received: by 2002:a05:6638:31c2:b0:35a:c5b1:b567 with SMTP id n2-20020a05663831c200b0035ac5b1b567mr4600630jav.58.1664551009140; Fri, 30 Sep 2022 08:16:49 -0700 (PDT) MIME-Version: 1.0 References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-11-rick.p.edgecombe@intel.com> In-Reply-To: <20220929222936.14584-11-rick.p.edgecombe@intel.com> From: Jann Horn Date: Fri, 30 Sep 2022 17:16:12 +0200 Message-ID: Subject: Re: [PATCH v2 10/39] x86/mm: Introduce _PAGE_COW To: Rick Edgecombe Cc: x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V . Shankar" , Weijiang Yang , "Kirill A . Shutemov" , joao.moreira@intel.com, John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, Yu-cheng Yu Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Fri, Sep 30, 2022 at 12:30 AM Rick Edgecombe wrote: > The reason it's lightly used is that Dirty=1 is normally set _before_ a > write. A write with a Write=0 PTE would typically only generate a fault, > not set Dirty=1. Hardware can (rarely) both set Write=1 *and* generate the > fault, resulting in a Dirty=0,Write=1 PTE. Hardware which supports shadow > stacks will no longer exhibit this oddity. Stupid question, since I just recently learned that IOMMUv2 is a thing: I assume this also holds for IOMMUs that implement IOMMUv2/SVA, where the IOMMU directly walks the userspace page tables, and not just for the CPU core?