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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,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 2E4FAC433E2 for ; Wed, 24 Mar 2021 19:18:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB5F461984 for ; Wed, 24 Mar 2021 19:18:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237878AbhCXTS1 (ORCPT ); Wed, 24 Mar 2021 15:18:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237929AbhCXTRO (ORCPT ); Wed, 24 Mar 2021 15:17:14 -0400 Received: from mail-wr1-x435.google.com (mail-wr1-x435.google.com [IPv6:2a00:1450:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6AD10C061763 for ; Wed, 24 Mar 2021 12:17:14 -0700 (PDT) Received: by mail-wr1-x435.google.com with SMTP id v11so25562324wro.7 for ; Wed, 24 Mar 2021 12:17:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to; bh=ks7ShY2KdqBCOa2qudGrTxafbstGO1KxoD94z5nmwd4=; b=bjZoBOViVyL1mHLmUFR7BSZIMAluKI/kXY5E2/ztjZRSCxzbzqraymTeP/LQuXxMd6 5YPx58H1VAuhSW12/DzOC9BHGHgBV1J/hhCob2AhjQhBoGcMDaLPjYwGaOGrtjITgpiU twnR7Di8AA6EdQ4WpfeSjtyjUfsAP9baelo+A= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :in-reply-to; bh=ks7ShY2KdqBCOa2qudGrTxafbstGO1KxoD94z5nmwd4=; b=Hy6pAo4w/7OkiYUtdDdaJ653auZQQY402Fd20GRTM7bvz4ya9iLRONxaeW2xHIQgAw 7Z8RYA+6uHDSdIzO0r4fydDCeSFeXiwSifk0brg1KE8+HPx++WH6BnUQ5eyzbc4wX0l2 ZyONbLc/JCI9gI/pUs0jQWRx+jM0Ytq1tmMB2U0c/l1Equv7t/ufclEb2GaMRlDK+yEp na87xPHo5Sl0qdi912G6q11NDnHHMriDm7jXGUif+YtXTFAG3z/DQmuCQvzQTKc/r5fn sf9RO5s8ZOtj5hBv7SYkZY9Y4aJ90cAqCmpE4xCgulgwUZkecfxsxvmEydNOcOplxiQG 4r7Q== X-Gm-Message-State: AOAM531DW1xPB4FliGxzh1sLfvLSXYND+WxIc8fG7CyNxLaxRQzAhJPp fdVJY3D+29mtnUJcRDL1ttGyMmGJQKqteWQ8 X-Google-Smtp-Source: ABdhPJz0jKYo0H/XBwWmbtO5rMA4MuyiBVo+Vi9lmrQcQ8si+ZT3Tkgf1DTxMp2/fnyfyvXSPQ76vg== X-Received: by 2002:a5d:6312:: with SMTP id i18mr5156957wru.149.1616613433126; Wed, 24 Mar 2021 12:17:13 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id f2sm3344574wmp.20.2021.03.24.12.17.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Mar 2021 12:17:12 -0700 (PDT) Date: Wed, 24 Mar 2021 20:17:10 +0100 From: Daniel Vetter To: Jason Gunthorpe Cc: Daniel Vetter , DRI Development , LKML , kvm@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, 3pvd@google.com, Jann Horn , Paolo Bonzini , Cornelia Huck , Peter Xu , Alex Williamson , Daniel Vetter Subject: Re: [PATCH 3/3] mm: unexport follow_pfn Message-ID: Mail-Followup-To: Jason Gunthorpe , DRI Development , LKML , kvm@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, 3pvd@google.com, Jann Horn , Paolo Bonzini , Cornelia Huck , Peter Xu , Alex Williamson , Daniel Vetter References: <20210316153303.3216674-1-daniel.vetter@ffwll.ch> <20210316153303.3216674-4-daniel.vetter@ffwll.ch> <20210324125211.GA2356281@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210324125211.GA2356281@nvidia.com> X-Operating-System: Linux phenom 5.7.0-1-amd64 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 24, 2021 at 09:52:11AM -0300, Jason Gunthorpe wrote: > On Tue, Mar 16, 2021 at 04:33:03PM +0100, Daniel Vetter wrote: > > Both kvm (in bd2fae8da794 ("KVM: do not assume PTE is writable after > > follow_pfn")) and vfio (in 07956b6269d3 ("vfio/type1: Use > > follow_pte()")) have lost their callsites of follow_pfn(). All the > > other ones have been switched over to unsafe_follow_pfn because they > > cannot be fixed without breaking userspace api. > > > > Argueably the vfio code is still racy, but that's kinda a bigger > > picture. But since it does leak the pte beyond where it drops the pt > > lock, without anything else like an mmu notifier guaranteeing > > coherence, the problem is at least clearly visible in the vfio code. > > So good enough with me. > > > > I've decided to keep the explanation that after dropping the pt lock > > you must have an mmu notifier if you keep using the pte somehow by > > adjusting it and moving it into the kerneldoc for the new follow_pte() > > function. > > > > Cc: 3pvd@google.com > > Cc: Jann Horn > > Cc: Paolo Bonzini > > Cc: Jason Gunthorpe > > Cc: Cornelia Huck > > Cc: Peter Xu > > Cc: Alex Williamson > > Cc: linux-mm@kvack.org > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: linux-samsung-soc@vger.kernel.org > > Cc: linux-media@vger.kernel.org > > Cc: kvm@vger.kernel.org > > Signed-off-by: Daniel Vetter > > --- > > include/linux/mm.h | 2 -- > > mm/memory.c | 26 +++++--------------------- > > mm/nommu.c | 13 +------------ > > 3 files changed, 6 insertions(+), 35 deletions(-) > > I think this is the right thing to do. Was just about to smash this into the topic branch for testing in linux-next. Feel like an ack on the series, or at least the two mm patches? -Daniel > > Alex is working on fixing VFIO and while kvm is still racy using > follow pte, I think they are working on it too? > > Jason -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch