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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 8437AC43387 for ; Thu, 20 Dec 2018 18:33:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 59081218D3 for ; Thu, 20 Dec 2018 18:33:17 +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="iVTpVsWN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389257AbeLTSdQ (ORCPT ); Thu, 20 Dec 2018 13:33:16 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:49996 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730556AbeLTSdP (ORCPT ); Thu, 20 Dec 2018 13:33:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=zWmImtXqeGkHvkoyDwKHxzBwzs1ZAXYh07e9ywdlueU=; b=iVTpVsWNGKhInzhT4FZQZfSxM r8e8WfaFO9H2N5Qu+9zsmvgvsKCzPRuzJR19wWQmV8jUgzVyYTYb/b+VEklSZdUj/lhq+j8J4iDkd jzvG2vmovGtxgZMPq2ArT1O6o1HUipsbNJrPHcL1fTk9m3TLWWgx8f9TfdMMPf4Hnaij+PplHSX8Z HvZ/2EbOZrkPsAw11IuMbQ8zlOtrHF5bcnOLBv7SPzDLyeOOoqkm1WQWUhPcVgUldipKFNWMXCCBZ BV3A67K/16dhdiIfHvyXmZ2RCMymyoRoCgj8cHDLGM26EeuWyR9DeNzd1vX2G9L1A3HazlaQlYQ1H nBPnrWPRg==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1ga38C-0005OU-2z; Thu, 20 Dec 2018 18:33:12 +0000 Date: Thu, 20 Dec 2018 10:33:11 -0800 From: Christoph Hellwig To: Daniel Vetter Cc: Christoph Hellwig , Oleksandr Andrushchenko , Juergen Gross , Oleksandr Andrushchenko , Linux Kernel Mailing List , dri-devel , Daniel Vetter , xen-devel@lists.xenproject.org, boris.ostrovsky@oracle.com Subject: Re: [PATCH] drm/xen-front: Make shmem backed display buffer coherent Message-ID: <20181220183311.GA30801@infradead.org> References: <20181127103252.20994-1-andr2000@gmail.com> <17640791-5306-f7e4-8588-dd39c14e975b@tronnes.org> <20181220153646.GA22997@infradead.org> <20181220173950.GA19641@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.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 Thu, Dec 20, 2018 at 07:29:37PM +0100, Daniel Vetter wrote: > What we most definitely not want to end up with though is actually > streaming dma, because with that all the zero copy buffer sharing > tricks become pointless. There's pretty epic amounts of hacks to work > around this, I have no idea what's supposed to give here. Err, with streaming DMA buffer sharing is trivial. The coherent DMA allocator is what causes all kinds of horrible hacks that can't actually work on various platforms.