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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 08698C433E0 for ; Tue, 16 Mar 2021 15:46:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 68A43650F7 for ; Tue, 16 Mar 2021 15:46:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 68A43650F7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E680D6B0085; Tue, 16 Mar 2021 11:46:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E18A66B0087; Tue, 16 Mar 2021 11:46:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CB9586B0088; Tue, 16 Mar 2021 11:46:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0230.hostedemail.com [216.40.44.230]) by kanga.kvack.org (Postfix) with ESMTP id AFCB76B0085 for ; Tue, 16 Mar 2021 11:46:46 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 6CED7180AD837 for ; Tue, 16 Mar 2021 15:46:46 +0000 (UTC) X-FDA: 77926165212.19.947D967 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf04.hostedemail.com (Postfix) with ESMTP id 3F8B93CB for ; Tue, 16 Mar 2021 15:46:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=nZWmZIikdIqUXKBumu57DbQjqCe7A1JBHSVghyYvFqQ=; b=dIrVhYw7bPP4ttWa7NL3R27MKa KyUD/H24QkdGcP9DuFv5nwIFtZqYGR6Ul0TltL3rD4JAouZuBCZ6lF5wkjxsV2rZVRQRZbpH4s7kI txtpJcRtrWpvFaJORU344KyNSyVvuzIVIDWMxlwXp7JdDiEIiX2p5RwEB2hwX2vvvlepE7KH4gnWH A5ZG0tnV4LVhQwnbQQBN1JuJglXk4e60N6FtZpxvjC93P35IwNo55p581YCbtRIIqEcIStoRO0Yoc lNkNkCjSg3BYK0cDWCItnKyPgKofzXiE4e3VJXF9Km+YyE0MbOvCeENKEqzIupAqH8Lh5nFMA/0h0 P237phhQ==; Received: from hch by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lMBtF-000FyW-8d; Tue, 16 Mar 2021 15:45:53 +0000 Date: Tue, 16 Mar 2021 15:45:49 +0000 From: Christoph Hellwig To: Daniel Vetter Cc: 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, Tomasz Figa , Hans Verkuil , Daniel Vetter , Jason Gunthorpe , Kees Cook , Dan Williams , Andrew Morton , John Hubbard , J??r??me Glisse , Jan Kara , Pawel Osciak , Marek Szyprowski , Kyungmin Park , Laurent Dufour , Vlastimil Babka , Daniel Jordan , Michel Lespinasse Subject: Re: [PATCH 2/3] media/videobuf1|2: Mark follow_pfn usage as unsafe Message-ID: <20210316154549.GA60450@infradead.org> References: <20210316153303.3216674-1-daniel.vetter@ffwll.ch> <20210316153303.3216674-3-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210316153303.3216674-3-daniel.vetter@ffwll.ch> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html X-Stat-Signature: kizk4zuxcfioeatof4u7c8qcwot76ej3 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 3F8B93CB Received-SPF: none (casper.srs.infradead.org>: No applicable sender policy available) receiver=imf04; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615909589-68668 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 Tue, Mar 16, 2021 at 04:33:02PM +0100, Daniel Vetter wrote: > The media model assumes that buffers are all preallocated, so that > when a media pipeline is running we never miss a deadline because the > buffers aren't allocated or available. > > This means we cannot fix the v4l follow_pfn usage through > mmu_notifier, without breaking how this all works. The only real fix > is to deprecate userptr support for VM_IO | VM_PFNMAP mappings and > tell everyone to cut over to dma-buf memory sharing for zerocopy. > > userptr for normal memory will keep working as-is, this only affects > the zerocopy userptr usage enabled in 50ac952d2263 ("[media] > videobuf2-dma-sg: Support io userptr operations on io memory"). Maybe I'm missing something, but wasn't the conclusion last time that this hackish early device to device copy support can just go away?