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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 F3D67C433E0 for ; Tue, 7 Jul 2020 15:14:51 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (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 C69B020771 for ; Tue, 7 Jul 2020 15:14:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C69B020771 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id A6E8586A84; Tue, 7 Jul 2020 15:14:51 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id TTjm_uYfi18S; Tue, 7 Jul 2020 15:14:49 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by fraxinus.osuosl.org (Postfix) with ESMTP id 198D186A3C; Tue, 7 Jul 2020 15:14:49 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 0F5BCC07FF; Tue, 7 Jul 2020 15:14:49 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id E2382C016F for ; Tue, 7 Jul 2020 15:14:47 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id D100A86A3C for ; Tue, 7 Jul 2020 15:14:47 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 6Fd3fpEHxfx0 for ; Tue, 7 Jul 2020 15:14:46 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by fraxinus.osuosl.org (Postfix) with ESMTPS id 9DEFD84C2C for ; Tue, 7 Jul 2020 15:14:46 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id E6E5268AFE; Tue, 7 Jul 2020 17:14:41 +0200 (CEST) Date: Tue, 7 Jul 2020 17:14:40 +0200 From: Christoph Hellwig To: Jonathan Lemon Subject: Re: [PATCH 1/4] dma-mapping: add a new dma_need_sync API Message-ID: <20200707151440.GA23816@lst.de> References: <20200629130359.2690853-1-hch@lst.de> <20200629130359.2690853-2-hch@lst.de> <20200706194227.vfhv5o4lporxjxmq@bsd-mbp.dhcp.thefacebook.com> <20200707064730.GA23602@lst.de> <20200707151109.qui5uzzzq4dihfie@bsd-mbp> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200707151109.qui5uzzzq4dihfie@bsd-mbp> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, bpf@vger.kernel.org, =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Christoph Hellwig , Magnus Karlsson X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Tue, Jul 07, 2020 at 08:11:09AM -0700, Jonathan Lemon wrote: > > You need to check every mapping. E.g. this API pairs with a > > dma_map_single/page call. For S/G mappings you'd need to call it for > > each entry, although if you have a use case for that we really should > > add a dma_sg_need_sync helper instea of open coding the scatterlist walk. > > My use case is setting up a pinned memory area, and caching the dma > mappings. I'd like to bypass storing the DMA addresses if they aren't > needed. For example: > > setup() > { > if (dma_need_sync(dev, addr, len)) { > kvmalloc_array(...) > cache_dma_mappings(...) > } > > > dev_get_dma(page) > { > if (!cache) > return page_to_phys(page) > > return dma_cache_lookup(...) > > > > The reason for doing it this way is that the page in question may be > backed by either system memory, or device memory such as a GPU. For the > latter, the GPU provides a table of DMA addresses where data may be > accessed, so I'm unable to use the dma_map_page() API. dma_need_sync doesn't tell you if the unmap needs the dma_addr_t. I've been think about replacing CONFIG_NEED_DMA_MAP_STATE with a runtime for a while, which would give you exattly what you need. For now it isn't very useful as there are very few configs left that do not have CONFIG_NEED_DMA_MAP_STATE set. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu