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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 0211CC7618B for ; Thu, 25 Jul 2019 14:10:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C7B2422C7C for ; Thu, 25 Jul 2019 14:10:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="yvFj1CUL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387766AbfGYOKq (ORCPT ); Thu, 25 Jul 2019 10:10:46 -0400 Received: from lelv0142.ext.ti.com ([198.47.23.249]:32830 "EHLO lelv0142.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387551AbfGYOKq (ORCPT ); Thu, 25 Jul 2019 10:10:46 -0400 Received: from fllv0035.itg.ti.com ([10.64.41.0]) by lelv0142.ext.ti.com (8.15.2/8.15.2) with ESMTP id x6PEAAd8113214; Thu, 25 Jul 2019 09:10:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1564063810; bh=mVv1nDWtq6/1PWlhIk1q4KK71i681umUf+79EFLyBFw=; h=Subject:To:CC:References:From:Date:In-Reply-To; b=yvFj1CULd+JqphxDYLptg+cY4QAlhkwlcybiAuiIpLD3ZiwvXbgwH46H2bL7zBrKv 36SFJLJLWpE//7+VGXqtssZKckCQ4+lQU6N7LvYNyYetXHpO3jmmesX0DyVKF0IYUn gYJErN5sBT/UMqrhxSj+M41yjqEkHuQxv/rAQyh8= Received: from DLEE108.ent.ti.com (dlee108.ent.ti.com [157.170.170.38]) by fllv0035.itg.ti.com (8.15.2/8.15.2) with ESMTPS id x6PEAAwj121944 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 25 Jul 2019 09:10:10 -0500 Received: from DLEE115.ent.ti.com (157.170.170.26) by DLEE108.ent.ti.com (157.170.170.38) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1713.5; Thu, 25 Jul 2019 09:10:10 -0500 Received: from lelv0327.itg.ti.com (10.180.67.183) by DLEE115.ent.ti.com (157.170.170.26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1713.5 via Frontend Transport; Thu, 25 Jul 2019 09:10:10 -0500 Received: from [10.250.86.29] (ileax41-snat.itg.ti.com [10.172.224.153]) by lelv0327.itg.ti.com (8.15.2/8.15.2) with ESMTP id x6PEA8Zk034771; Thu, 25 Jul 2019 09:10:09 -0500 Subject: Re: [PATCH v6 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps To: Christoph Hellwig CC: John Stultz , lkml , Laura Abbott , Benjamin Gaignard , Sumit Semwal , Liam Mark , Pratik Patel , Brian Starkey , Vincent Donnefort , Sudipto Paul , Xu YiPing , "Chenfeng (puck)" , butao , "Xiaqing (A)" , Yudongbin , Chenbo Feng , Alistair Strachan , dri-devel References: <20190624194908.121273-1-john.stultz@linaro.org> <20190624194908.121273-5-john.stultz@linaro.org> <20190718100840.GB19666@infradead.org> <20190724065958.GC16225@infradead.org> <8e6f8e4f-20fc-1f1f-2228-f4fd7c7c5c1f@ti.com> <20190725125014.GD20286@infradead.org> <0eae0024-1fdf-bd06-a8ff-1a41f0af3c69@ti.com> <20190725140448.GA25010@infradead.org> From: "Andrew F. Davis" Message-ID: <8e2ec315-5d18-68b2-8cb5-2bfb8a116d1b@ti.com> Date: Thu, 25 Jul 2019 10:10:08 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190725140448.GA25010@infradead.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/25/19 10:04 AM, Christoph Hellwig wrote: > On Thu, Jul 25, 2019 at 09:31:50AM -0400, Andrew F. Davis wrote: >> But that's just it, dma-buf does not assume buffers are backed by normal >> kernel managed memory, it is up to the buffer exporter where and when to >> allocate the memory. The memory backed by this SRAM buffer does not have >> the normal struct page backing. So moving the map, sync, etc functions >> to common code would fail for this and many other heap types. This was a >> major problem with Ion that prompted this new design. > > The code clearly shows it has page backing, e.g. this: > > + sg_set_page(table->sgl, pfn_to_page(PFN_DOWN(buffer->paddr)), buffer->len, 0); > > and the fact that it (and the dma-buf API) uses scatterlists, which > requires pages. > Pages yes, but not "normal" pages from the kernel managed area. page_to_pfn() will return bad values on the pages returned by this allocator and so will any of the kernel sync/map functions. Therefor those operations cannot be common and need special per-heap handling. Andrew