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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0F0F0C2BD09 for ; Fri, 12 Jul 2024 04:54:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=hdkSprgXz1TOuzpRa551TU4TlZl7jkQZWLDN1cGr7Gs=; b=qFRsv2yGZOvQVMMx6nrjz8y8l9 ZYUg5SVaDFoqAKdI9/l/ahxcUM5YLzKrhyVXbjSzaOCtvrNn97qIFqtOShhH4WAV5ulHz7srPvoJK kikyvwVgE0E0e6H2/fCPMBjkNqSNwixo9F8kxFgr6E2qhyY8aVprdNe9YhB7y8hSs/WAuDv+E+jWW WhubBvM1kmIyuHAeWRtLJNdJrk532ptvLMAqZHe3S8z1vuEYnneiqD5dXK60JhxouQgZPOxs3KdsQ r90NicWT5Yna4hmFRG0LNJaUYUK6y6pV+kYU3x4Q55U1gofv8MjHNSJxUy0daLYWMEN5wLlNwQDcB wX89cYbA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sS8Io-0000000GQGu-1vYc; Fri, 12 Jul 2024 04:54:38 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sS8Il-0000000GQDS-2Y2L for linux-nvme@lists.infradead.org; Fri, 12 Jul 2024 04:54:37 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 1F8DD68BEB; Fri, 12 Jul 2024 06:54:23 +0200 (CEST) Date: Fri, 12 Jul 2024 06:54:22 +0200 From: Christoph Hellwig To: Jason Gunthorpe Cc: Christoph Hellwig , Leon Romanovsky , Jens Axboe , Robin Murphy , Joerg Roedel , Will Deacon , Keith Busch , "Zeng, Oak" , Chaitanya Kulkarni , Sagi Grimberg , Bjorn Helgaas , Logan Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , Marek Szyprowski , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrew Morton , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, iommu@lists.linux.dev, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v1 00/18] Provide a new two step DMA API mapping API Message-ID: <20240712045422.GA4774@lst.de> References: <20240705063910.GA12337@lst.de> <20240708235721.GF14050@ziepe.ca> <20240709062015.GB16180@lst.de> <20240709190320.GN14050@ziepe.ca> <20240710062212.GA25895@lst.de> <20240711232917.GR14050@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240711232917.GR14050@ziepe.ca> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240711_215435_812370_63846AA7 X-CRM114-Status: GOOD ( 16.71 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Thu, Jul 11, 2024 at 08:29:17PM -0300, Jason Gunthorpe wrote: > So this little detail needs to be taken care of somehow as well, and I > didn't see it in this RFC. Yes. Same about generally not mixing P2P and non-P2P. > > > For the block layer just having one kind per BIO is fine right now, > > although I could see use cases where people would want to combine > > them. We can probably defer that until it is needed, though. > > Do you have an application in mind that would want multi-kind per BIO? If you are doing say garbage collection in a file system, and do write that sources data from multiple devices, where some sit directly on the root port and others behind a switch. This is all purely hypothetical, and I'm happy to just check for it and reject it for it now.