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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 47BA1C43603 for ; Wed, 4 Dec 2019 14:16:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E12512077B for ; Wed, 4 Dec 2019 14:16:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=shipmail.org header.i=@shipmail.org header.b="rZAHpK0e" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E12512077B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shipmail.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 52AEA6B0AF7; Wed, 4 Dec 2019 09:16:20 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B52B6B0AF8; Wed, 4 Dec 2019 09:16:20 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 37B996B0AF9; Wed, 4 Dec 2019 09:16:20 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0087.hostedemail.com [216.40.44.87]) by kanga.kvack.org (Postfix) with ESMTP id 1CCA66B0AF7 for ; Wed, 4 Dec 2019 09:16:20 -0500 (EST) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id D4F7A52B7 for ; Wed, 4 Dec 2019 14:16:19 +0000 (UTC) X-FDA: 76227658878.06.uncle18_8e55cfe66de50 X-HE-Tag: uncle18_8e55cfe66de50 X-Filterd-Recvd-Size: 4891 Received: from pio-pvt-msa2.bahnhof.se (pio-pvt-msa2.bahnhof.se [79.136.2.41]) by imf23.hostedemail.com (Postfix) with ESMTP for ; Wed, 4 Dec 2019 14:16:18 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by pio-pvt-msa2.bahnhof.se (Postfix) with ESMTP id 404F63F47A; Wed, 4 Dec 2019 15:16:16 +0100 (CET) Authentication-Results: pio-pvt-msa2.bahnhof.se; dkim=pass (1024-bit key; unprotected) header.d=shipmail.org header.i=@shipmail.org header.b=rZAHpK0e; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at bahnhof.se Received: from pio-pvt-msa2.bahnhof.se ([127.0.0.1]) by localhost (pio-pvt-msa2.bahnhof.se [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Km9YbJabySxh; Wed, 4 Dec 2019 15:16:15 +0100 (CET) Received: from mail1.shipmail.org (h-205-35.A357.priv.bahnhof.se [155.4.205.35]) (Authenticated sender: mb878879) by pio-pvt-msa2.bahnhof.se (Postfix) with ESMTPA id B12EC3F435; Wed, 4 Dec 2019 15:16:10 +0100 (CET) Received: from localhost.localdomain (h-205-35.A357.priv.bahnhof.se [155.4.205.35]) by mail1.shipmail.org (Postfix) with ESMTPSA id CC96A360608; Wed, 4 Dec 2019 15:16:09 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=shipmail.org; s=mail; t=1575468969; bh=6lPiouUhoiffGwUD7wWb3htpX7yUG7AcztUp9kFYLLI=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=rZAHpK0eBRbwsu388vybVwAbkZPQbHLOKHyty+7r1UkSH/04RpXI227bMqMFVxlRP UrWX6Ijp3UQj9Wj1JrcokDlB6PmEsywz/A8GWJ0k+N90X8OolmzmVQX97MzB97QuBG Cuz7tDkgVF3SLv9OwcbU14195XaWJKO0qK8uDafY= Subject: Re: [PATCH v2 2/2] drm/ttm: Fix vm page protection handling To: Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, pv-drivers@vmware.com, linux-graphics-maintainer@vmware.com, Thomas Hellstrom , Andrew Morton , "Matthew Wilcox (Oracle)" , "Kirill A. Shutemov" , Ralph Campbell , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , =?UTF-8?Q?Christian_K=c3=b6nig?= References: <20191203104853.4378-1-thomas_os@shipmail.org> <20191203104853.4378-3-thomas_os@shipmail.org> <20191204135219.GH25242@dhcp22.suse.cz> From: =?UTF-8?Q?Thomas_Hellstr=c3=b6m_=28VMware=29?= Organization: VMware Inc. Message-ID: Date: Wed, 4 Dec 2019 15:16:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20191204135219.GH25242@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12/4/19 2:52 PM, Michal Hocko wrote: > On Tue 03-12-19 11:48:53, Thomas Hellstr=C3=B6m (VMware) wrote: >> From: Thomas Hellstrom >> >> TTM graphics buffer objects may, transparently to user-space, move >> between IO and system memory. When that happens, all PTEs pointing to = the >> old location are zapped before the move and then faulted in again if >> needed. When that happens, the page protection caching mode- and >> encryption bits may change and be different from those of >> struct vm_area_struct::vm_page_prot. >> >> We were using an ugly hack to set the page protection correctly. >> Fix that and instead use vmf_insert_mixed_prot() and / or >> vmf_insert_pfn_prot(). >> Also get the default page protection from >> struct vm_area_struct::vm_page_prot rather than using vm_get_page_prot= (). >> This way we catch modifications done by the vm system for drivers that >> want write-notification. > So essentially this should have any new side effect on functionality it > is just making a hacky/ugly code less so? Functionality is unchanged. The use of a on-stack vma copy was severely=20 frowned upon in an earlier thread, which also points to another similar=20 example using vmf_insert_pfn_prot(). https://lore.kernel.org/lkml/20190905103541.4161-2-thomas_os@shipmail.org= / > In other words what are the > consequences of having page protection inconsistent from vma's? During the years, it looks like the caching- and encryption flags of=20 vma::vm_page_prot have been largely removed from usage. From what I can=20 tell, there are no more places left that can affect TTM. We discussed=20 __split_huge_pmd_locked() towards the end of that thread, but that=20 doesn't affect TTM even with huge page-table entries. /Thomas