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=-3.8 required=3.0 tests=BAYES_00, 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 BE14BC433DB for ; Wed, 13 Jan 2021 21:10:29 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2D5B42310A for ; Wed, 13 Jan 2021 21:10:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2D5B42310A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id F33BF6EC68; Wed, 13 Jan 2021 21:10:25 +0000 (UTC) Received: from fireflyinternet.com (unknown [77.68.26.236]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8A9DB6EC65; Wed, 13 Jan 2021 21:10:23 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from localhost (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP (TLS) id 23589380-1500050 for multiple; Wed, 13 Jan 2021 21:08:56 +0000 MIME-Version: 1.0 In-Reply-To: References: <20210113140604.3615437-1-daniel.vetter@ffwll.ch> <161055261490.6195.7986280621869334351@build.alporthouse.com> Subject: Re: [Intel-gfx] [PATCH] drm-buf: Add debug option From: Chris Wilson To: Daniel Vetter Date: Wed, 13 Jan 2021 21:08:54 +0000 Message-ID: <161057213487.6195.581396740566956696@build.alporthouse.com> User-Agent: alot/0.9 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Intel Graphics Development , DRI Development , Christian König , DMA BUFFER SHARING FRAMEWORK , David Stevens , Daniel Vetter , DMA BUFFER SHARING FRAMEWORK Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Quoting Daniel Vetter (2021-01-13 20:50:11) > On Wed, Jan 13, 2021 at 4:43 PM Chris Wilson wrote: > > > > Quoting Daniel Vetter (2021-01-13 14:06:04) > > > We have too many people abusing the struct page they can get at but > > > really shouldn't in importers. Aside from that the backing page might > > > simply not exist (for dynamic p2p mappings) looking at it and using it > > > e.g. for mmap can also wreak the page handling of the exporter > > > completely. Importers really must go through the proper interface like > > > dma_buf_mmap for everything. > > > > If the exporter doesn't want to expose the struct page, why are they > > setting it in the exported sg_table? > > You need to store it somewhere, otherwise the dma-api doesn't work. > Essentially this achieves clearing/resetting the struct page pointer, > without additional allocations somewhere, or tons of driver changes > (since presumably the driver does keep track of the struct page > somewhere too). Only for mapping, and that's before the export -- if there's even a struct page to begin with. > Also as long as we have random importers looking at struct page we > can't just remove it, or crashes everywhere. So it has to be some > debug option you can disable. Totally agreed that nothing generic can rely on pages being transported via dma-buf, and memfd is there if you do want a suitable transport. The one I don't know about is dma-buf heap, do both parties there consent to transport pages via the dma-buf? i.e. do they have special cases for import/export between heaps? -Chris _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel