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=-15.7 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 AF1BAC43462 for ; Thu, 8 Apr 2021 11:44:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7CC8261157 for ; Thu, 8 Apr 2021 11:44:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231381AbhDHLoY (ORCPT ); Thu, 8 Apr 2021 07:44:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231451AbhDHLoW (ORCPT ); Thu, 8 Apr 2021 07:44:22 -0400 Received: from mail-wr1-x42e.google.com (mail-wr1-x42e.google.com [IPv6:2a00:1450:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D166C061763 for ; Thu, 8 Apr 2021 04:44:10 -0700 (PDT) Received: by mail-wr1-x42e.google.com with SMTP id x7so1777953wrw.10 for ; Thu, 08 Apr 2021 04:44:10 -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=+bIMHjM8IkWGQ9w2UhAWL6nad3z/nsAAXwfEZIX9lWc=; b=HzLW9PAKd4D2FBBBl8PCr0y3Kw+mUxzAfMkhunUFy5g084vTc3tR3FgCZULEQo0aRJ 70RJkyKfjoUXms2whB0E+fWJOI2bfvz4DeQho9AoZyPY+Fi8PJLOMkNvY/vNEMPUQWqq eGGIn6Fb7N4Gn6wTADCQI6woEj7GonRXHLLvE= 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=+bIMHjM8IkWGQ9w2UhAWL6nad3z/nsAAXwfEZIX9lWc=; b=A7NOWdZBRGCaElffiyO8au+cC9OpdO+DLgG2RRBlzTZl0nQvL+YU19y4gniaEbO4Xa pPZ4jD2gH0oNL0vB1xIB3K3pHAWoaA/+83BPSparXOJV0P8PzkGSCygUx4S8zfdT1BWp Y2xWomf6nvB6n7FvUd6YIMaefv4HYkfY2123QyQAwBKSo3yUC2UZRNTtTkrt4sfAWn0X SGLLRQctYK3HguhIDOENiFzc4lzZat9y1r3sbRD9Xw7F4BVloqySWwJO8QwPdBkB6Inx NEWotjA7/XOfKzRIcS1xolUoQpDxGDhg/Oy+mnyb3SkATnPJmcBwk0u9myv0YR4bgGVe cLnw== X-Gm-Message-State: AOAM532HufBGxIMKcW/GCN/xCyrf7xF1ytqoSH3/eQ2zggKnnZV9PfZb J1IVVhQDV9HI4p+tVKPSch0wdw== X-Google-Smtp-Source: ABdhPJx7T3RCQlE5ua8yXfZvWLP1S80e0mDHoUGS7ErWGxP0VUT/3ngstw02CFjw7tqjgD8X14d31A== X-Received: by 2002:adf:e743:: with SMTP id c3mr7764889wrn.408.1617882248844; Thu, 08 Apr 2021 04:44:08 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id f7sm11692950wmq.11.2021.04.08.04.44.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Apr 2021 04:44:08 -0700 (PDT) Date: Thu, 8 Apr 2021 13:44:06 +0200 From: Daniel Vetter To: Paolo Bonzini Cc: 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 , Cornelia Huck , Peter Xu , Alex Williamson , Daniel Vetter Subject: Re: [PATCH 3/3] mm: unexport follow_pfn Message-ID: Mail-Followup-To: Paolo Bonzini , 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 , Cornelia Huck , Peter Xu , Alex Williamson , Daniel Vetter References: <20210316153303.3216674-1-daniel.vetter@ffwll.ch> <20210316153303.3216674-4-daniel.vetter@ffwll.ch> <20210329133101.GA1168973@nvidia.com> <5f956a46-da38-e72a-edaa-3b746a275f1e@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5f956a46-da38-e72a-edaa-3b746a275f1e@redhat.com> X-Operating-System: Linux phenom 5.7.0-1-amd64 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Thu, Apr 08, 2021 at 01:40:59PM +0200, Paolo Bonzini wrote: > On 08/04/21 12:05, Daniel Vetter wrote: > > On Mon, Mar 29, 2021 at 10:31:01AM -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 > > > > > > vfio and kvm > > > > Hm I thought kvm is non-racy due to the mmu notifier catch races? > > No, but the plan is indeed to have some struct for each page that uses > follow_pfn and update it from the MMU notifiers. Thanks for clarifying, I've fixed the commit message to mention both vfio and kvm as Jason suggested. I didn't know that the follow_pte usage in kvm still has some gaps wrt what's invalidated with mmu notifiers. Thanks, Daniel > > Paolo > > > > > > > > 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(-) > > > > > > Reviewed-by: Jason Gunthorpe > > > > Thanks for your r-b tags, I'll add them. > > -Daniel > > > > > > > > Jason > > > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch