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=-5.2 required=3.0 tests=BAYES_00, 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 A5672C43461 for ; Tue, 15 Sep 2020 06:36:29 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (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 3378A2076C for ; Tue, 15 Sep 2020 06:36:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3378A2076C 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 hemlock.osuosl.org (Postfix) with ESMTP id 062CE8702C; Tue, 15 Sep 2020 06:36:28 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id BF6ULmW5tb0c; Tue, 15 Sep 2020 06:36:26 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id 09D5E87093; Tue, 15 Sep 2020 06:36:26 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id D7BDAC0864; Tue, 15 Sep 2020 06:36:25 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 618CEC0051 for ; Tue, 15 Sep 2020 06:36:24 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 4219D863E8 for ; Tue, 15 Sep 2020 06:36:24 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 6kpn4wxVM5ya for ; Tue, 15 Sep 2020 06:36:23 +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 whitealder.osuosl.org (Postfix) with ESMTPS id 01792865CF for ; Tue, 15 Sep 2020 06:36:22 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id CFEFC6736F; Tue, 15 Sep 2020 08:36:18 +0200 (CEST) Date: Tue, 15 Sep 2020 08:36:18 +0200 From: Christoph Hellwig To: Matthew Wilcox Subject: Re: a saner API for allocating DMA addressable pages v2 Message-ID: <20200915063618.GD19113@lst.de> References: <20200914144433.1622958-1-hch@lst.de> <20200914152617.GR6583@casper.infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200914152617.GR6583@casper.infradead.org> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: alsa-devel@alsa-project.org, linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org, "James E.J. Bottomley" , linux-mm@kvack.org, linux1394-devel@lists.sourceforge.net, Christoph Hellwig , linux-samsung-soc@vger.kernel.org, Joonyoung Shim , linux-scsi@vger.kernel.org, Ben Skeggs , Matt Porter , linux-media@vger.kernel.org, Mauro Carvalho Chehab , linux-arm-kernel@lists.infradead.org, Thomas Bogendoerfer , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim , linux-mips@vger.kernel.org, iommu@lists.linux-foundation.org, Stefan Richter 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 Mon, Sep 14, 2020 at 04:26:17PM +0100, Matthew Wilcox wrote: > On Mon, Sep 14, 2020 at 04:44:16PM +0200, Christoph Hellwig wrote: > > I'm still a little unsure about the API naming, as alloc_pages sort of > > implies a struct page return value, but we return a kernel virtual > > address. > > Erm ... dma_alloc_pages() returns a struct page, so is this sentence > stale? Yes. > You say that like it's a bad thing. I think the problem is more that > people don't understand what non-coherent means and think they're > supporting it when they're not. > > dma_alloc_manual_flushing()? That sounds pretty awkward.. > > > As a follow up I plan to move the implementation of the > > DMA_ATTR_NO_KERNEL_MAPPING flag over to this framework as well, given > > that is also is a fundamentally non coherent allocation. The replacement > > for that flag would then return a struct page, as it is allowed to > > actually return pages without a kernel mapping as the name suggested > > (although most of the time they will actually have a kernel mapping..) > > If the page doesn't have a kernel mapping, shouldn't it return a PFN > or a phys_addr? Most APIs we'll feed it into need a struct page. The difference is just that it can be a highmem page. And if we want to get fancy we could change the kernel mapping to PROT_NONE eventually. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu