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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1AEBDC5475B for ; Wed, 6 Mar 2024 16:14:48 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A00BF6B0080; Wed, 6 Mar 2024 11:14:47 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9B1A96B0082; Wed, 6 Mar 2024 11:14:47 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8790C6B0083; Wed, 6 Mar 2024 11:14:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 78C066B0080 for ; Wed, 6 Mar 2024 11:14:47 -0500 (EST) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 34614120B28 for ; Wed, 6 Mar 2024 16:14:47 +0000 (UTC) X-FDA: 81867112614.29.4860A06 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf03.hostedemail.com (Postfix) with ESMTP id 0FC3B2002B for ; Wed, 6 Mar 2024 16:14:44 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=none; spf=pass (imf03.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1709741685; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OzO/9AzUna+R5zeXsIy0wzPXoaVBkJN8YgW56YBfzG4=; b=nUtrjUfvb7vCvUPzBdXeSyLiQEcyCnMws38A9oPsGw+XTlLSTQOmViGPZwHKUaJDPEj9do NCrwHfLTvzSMNM2AuzItXWGADRh+oIp5SH9UvZR+Pihljiqctf7sI6hT9Qjkb9RkENr+qp /1U0UFLdMuB9qA6ejwNgzorxn7lhwgA= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1709741685; a=rsa-sha256; cv=none; b=rRG6vE1TeLI/VvB3AIU3cGuCnMO5iDSG5TVBalHZE7qPAOW+UnvZcpRHPEFEcNgH7BFEbT n6YotlpPjjR+fE7Z23MGwL/1ssCVAubLbFkA9V1aFP6yd31nhSLzv+PBnR5aNDH0jqLYOm ZfilTM/y92ooRFA035/eCeqDOTrI/do= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=none; spf=pass (imf03.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de; dmarc=none Received: by verein.lst.de (Postfix, from userid 2407) id 339E968C4E; Wed, 6 Mar 2024 17:14:39 +0100 (CET) Date: Wed, 6 Mar 2024 17:14:38 +0100 From: Christoph Hellwig To: Jason Gunthorpe Cc: Christoph Hellwig , Keith Busch , Leon Romanovsky , Robin Murphy , Marek Szyprowski , Joerg Roedel , Will Deacon , Chaitanya Kulkarni , Chaitanya Kulkarni , Jonathan Corbet , Jens Axboe , Sagi Grimberg , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, iommu@lists.linux.dev, linux-nvme@lists.infradead.org, kvm@vger.kernel.org, linux-mm@kvack.org, Bart Van Assche , Damien Le Moal , Amir Goldstein , "josef@toxicpanda.com" , "Martin K. Petersen" , "daniel@iogearbox.net" , Dan Williams , "jack@suse.com" , Leon Romanovsky , Zhu Yanjun Subject: Re: [RFC RESEND 16/16] nvme-pci: use blk_rq_dma_map() for NVMe SGL Message-ID: <20240306161438.GA28427@lst.de> References: <016fc02cbfa9be3c156a6f74df38def1e09c08f1.1709635535.git.leon@kernel.org> <20240306143321.GA19711@lst.de> <20240306150518.GL9225@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240306150518.GL9225@ziepe.ca> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Queue-Id: 0FC3B2002B X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 37ejbxp9aqmqktaadnauc7d4hqhm1ue3 X-HE-Tag: 1709741684-255815 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 06, 2024 at 11:05:18AM -0400, Jason Gunthorpe wrote: > > Yes. And this whole proposal also seems clearly confused (not just > > because of the gazillion reposts) but because it mixes up the case > > where we can coalesce CPU regions into a single dma_addr_t range > > (iommu and maybe in the future swiotlb) and one where we need a > > I had the broad expectation that the DMA API user would already be > providing a place to store the dma_addr_t as it has to feed that into > the HW. That memory should simply last up until we do dma unmap and > the cases that need dma_addr_t during unmap can go get it from there. Well. The dma_addr_t needs to be fed into the hardware somehow obviously. But for a the coalesced case we only need one such field, not Nranges. > We can't do much on the map side as single range doesn't imply > contiguous range, P2P and alignment create discontinuities in the > dma_addr_t that still have to be delt with. For alignment the right answer is almost always to require the upper layers to align to the iommu granularity. We've been a bit lax about that due to the way scatterlists are designed, but requiring the proper alignment actually benefits everyone.