From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx146.postini.com [74.125.245.146]) by kanga.kvack.org (Postfix) with SMTP id B583A6B004D for ; Mon, 19 Dec 2011 01:17:01 -0500 (EST) Received: by mail-vx0-f174.google.com with SMTP id fk14so5402828vcb.33 for ; Sun, 18 Dec 2011 22:17:01 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <201112121648.52126.arnd@arndb.de> References: <1322816252-19955-1-git-send-email-sumit.semwal@ti.com> <20111209142405.6f371be6@pyramind.ukuu.org.uk> <201112121648.52126.arnd@arndb.de> From: "Semwal, Sumit" Date: Mon, 19 Dec 2011 11:46:40 +0530 Message-ID: Subject: Re: [Linaro-mm-sig] [RFC v2 1/2] dma-buf: Introduce dma buffer sharing mechanism Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Arnd Bergmann Cc: Daniel Vetter , Alan Cox , 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 Hi Arnd, Daniel, On Mon, Dec 12, 2011 at 10:18 PM, Arnd Bergmann wrote: > 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. I didn't see a consensus on whether dma_buf should enforce some form of serialization within the API - so atleast for v1 of dma-buf, I propose to 'not' impose a restriction, and we can tackle it (add new ops or enforce as design?) whenever we see the first need of it - will that be ok? [I am bending towards the thought that it is a problem to solve at a bigger platform than dma_buf.] > > =A0 =A0 =A0 =A0Arnd Best regards, ~Sumit. > > -- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org