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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 91F06C43461 for ; Tue, 8 Sep 2020 05:55:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3B642218AC for ; Tue, 8 Sep 2020 05:55:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="PwJlaz8Q" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728889AbgIHFzU (ORCPT ); Tue, 8 Sep 2020 01:55:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728531AbgIHFzQ (ORCPT ); Tue, 8 Sep 2020 01:55:16 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CD299C061573 for ; Mon, 7 Sep 2020 22:55:15 -0700 (PDT) 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=S3ldECwV6aYVj8kFvW2tKZDE9/xw5MtcF6dMvAAzlgk=; b=PwJlaz8QSQA8PmEsdT/oEaZTXP ybFVlLL+6NodzFFNNFhCkvJoI/2GqgQmwf0qU3lL9ljNCgMfVnL+9OubVVmnvsaKQGiXmaOCmfykA 6tyQ9TLS/LgF/mbnW8+YfiBKz8RdibDRYPaIdUsSX36o/zYxmUJijjHKll8nWoGOq6b0TD++EtI+j 0U4SS7my6/Cah3C7yLeF3v2knnA3X9WwbpTiRr0rW5bFYo3UxCSdWrtBdJO/lacNS0WCm9RGY8PEK ZkEqbNlf9pFfq0IAtR3PK40VroF4oi20xKozo26cC8mqcPqXaqG/dDWKVgLzwIPQwgtnmJqgTXsE4 L3M7KigA==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kFWb0-00057I-8N; Tue, 08 Sep 2020 05:55:10 +0000 Date: Tue, 8 Sep 2020 06:55:10 +0100 From: Christoph Hellwig To: Tom Murphy Cc: intel-gfx@lists.freedesktop.org, Joonas Lahtinen , Linux Kernel Mailing List , Jani Nikula , Christoph Hellwig , iommu@lists.linux-foundation.org, Rodrigo Vivi , David Woodhouse Subject: Re: [PATCH V2 5/5] DO NOT MERGE: iommu: disable list appending in dma-iommu Message-ID: <20200908055510.GA19078@infradead.org> References: <20200903201839.7327-1-murphyt7@tcd.ie> <20200903201839.7327-6-murphyt7@tcd.ie> <20200907070035.GA25114@infradead.org> <20200908053619.GA15418@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200908053619.GA15418@infradead.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 08, 2020 at 06:36:19AM +0100, Christoph Hellwig wrote: > On Mon, Sep 07, 2020 at 09:18:50PM +0100, Tom Murphy wrote: > > Yeah we talked about passing an attr to map_sg to disable merging at > > the following microconfernce: > > https://linuxplumbersconf.org/event/7/contributions/846/ > > As far as I can remember everyone seemed happy with that solution. I > > won't be working on this though as I don't have any more time to > > dedicate to this. It seems Lu Baolu will take over this. > > I'm absolutely again passing a flag. Tha just invites further > abuse. We need a PCI ID based quirk or something else that can't > be as easily abused. Also, I looked at i915 and there are just three dma_map_sg callers. The two dmabuf related ones are fixed by Marek in his series, leaving just the one in i915_gem_gtt_prepare_pages, which does indeed look very fishy. But if that one is so hard to fix it can just be replaced by an open coded for_each_sg loop that contains manual dma_map_page calls.