From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753358Ab1LLQtO (ORCPT ); Mon, 12 Dec 2011 11:49:14 -0500 Received: from moutng.kundenserver.de ([212.227.17.9]:56954 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751461Ab1LLQtM (ORCPT ); Mon, 12 Dec 2011 11:49:12 -0500 From: Arnd Bergmann To: Daniel Vetter Subject: Re: [Linaro-mm-sig] [RFC v2 1/2] dma-buf: Introduce dma buffer sharing mechanism Date: Mon, 12 Dec 2011 16:48:51 +0000 User-Agent: KMail/1.12.2 (Linux/3.2.0-rc1+; KDE/4.3.2; x86_64; ; ) Cc: Alan Cox , "Semwal, Sumit" , linux@arm.linux.org.uk, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <1322816252-19955-1-git-send-email-sumit.semwal@ti.com> <20111209142405.6f371be6@pyramind.ukuu.org.uk> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201112121648.52126.arnd@arndb.de> X-Provags-ID: V02:K0:IRDXWEcZRwkEuTQoYC1X6f5e+mAnK4Xpy85lu3bFmUO k8gOuIMCWcGbz1eaeWezr1NHUp/UKGz4i0B1MvwD7A/temGaoK UxgXriYQttq3v5YEB42TIKBtYpKoc/umPw2zIk0u/8hl+LNsa+ BkFT5SOkjRyjJhlIAgbLuxQY+D7rPAJa3qe9ttfyB2HC1BH2+N +DBu5TZDb6QME69MKMMW/Aat7WMIyXtL/5V/b499JiTsVaCptn Dd3i98U+nBrE6vhy7uHx0bTFaJeijAk5V92Q2Hm6TWq+CzC5ur hzeb50W7raLVm8K/GyUkpRKFnqE2SEqBcEFhqs6udQu3Flzjkn qnqKbF7OUwv2eQFARUCY= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Saturday 10 December 2011, Daniel Vetter wrote: > If userspace (through some driver calls) > tries to do stupid things, it'll just get garbage. See > Message-ID: > for my reasons why it think this is the right way to go forward. So in > essence I'm really interested in the reasons why you want the kernel > to enforce this (or I'm completely missing what's the contentious > issue here). This has nothing to do with user space mappings. Whatever user space does, you get garbage if you don't invalidate cache lines that were introduced through speculative prefetching before you access cache lines that were DMA'd from a device. Arnd