Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933961AbbBCHrh (ORCPT ); Tue, 3 Feb 2015 02:47:37 -0500 Received: from mail-wi0-f180.google.com ([209.85.212.180]:33523 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755058AbbBCHrf (ORCPT ); Tue, 3 Feb 2015 02:47:35 -0500 Date: Tue, 3 Feb 2015 08:48:56 +0100 From: Daniel Vetter To: Rob Clark Cc: Russell King - ARM Linux , Sumit Semwal , LKML , "linux-media@vger.kernel.org" , DRI mailing list , Linaro MM SIG Mailman List , "linux-arm-kernel@lists.infradead.org" , "linux-mm@kvack.org" , Linaro Kernel Mailman List , Tomasz Stanislawski , Robin Murphy , Marek Szyprowski , Daniel Vetter Subject: Re: [RFCv3 2/2] dma-buf: add helpers for sharing attacher constraints with dma-parms Message-ID: <20150203074856.GF14009@phenom.ffwll.local> Mail-Followup-To: Rob Clark , Russell King - ARM Linux , Sumit Semwal , LKML , "linux-media@vger.kernel.org" , DRI mailing list , Linaro MM SIG Mailman List , "linux-arm-kernel@lists.infradead.org" , "linux-mm@kvack.org" , Linaro Kernel Mailman List , Tomasz Stanislawski , Robin Murphy , Marek Szyprowski References: <1422347154-15258-1-git-send-email-sumit.semwal@linaro.org> <1422347154-15258-2-git-send-email-sumit.semwal@linaro.org> <20150129143908.GA26493@n2100.arm.linux.org.uk> <20150129154718.GB26493@n2100.arm.linux.org.uk> <20150129192610.GE26493@n2100.arm.linux.org.uk> <20150202165405.GX14009@phenom.ffwll.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: Linux phenom 3.16-2-amd64 User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1658 Lines: 35 On Mon, Feb 02, 2015 at 03:30:21PM -0500, Rob Clark wrote: > On Mon, Feb 2, 2015 at 11:54 AM, Daniel Vetter wrote: > >> My initial thought is for dma-buf to not try to prevent something than > >> an exporter can actually do.. I think the scenario you describe could > >> be handled by two sg-lists, if the exporter was clever enough. > > > > That's already needed, each attachment has it's own sg-list. After all > > there's no array of dma_addr_t in the sg tables, so you can't use one sg > > for more than one mapping. And due to different iommu different devices > > can easily end up with different addresses. > > > Well, to be fair it may not be explicitly stated, but currently one > should assume the dma_addr_t's in the dmabuf sglist are bogus. With > gpu's that implement per-process/context page tables, I'm not really > sure that there is a sane way to actually do anything else.. Hm, what does per-process/context page tables have to do here? At least on i915 we have a two levels of page tables: - first level for vm/device isolation, used through dma api - 2nd level for per-gpu-context isolation and context switching, handled internally. Since atm the dma api doesn't have any context of contexts or different pagetables, I don't see who you could use that at all. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/