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 1CAFBC433EF for ; Wed, 6 Jul 2022 06:51:46 +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=U7HTFOsPYHoY2+jtInKvQNIromPx7OWzOgUegE3v3Nk=; b=11riu3rLaImB7EVuUyDbTYXTFN IF48/OE6GF5Dkxlt546Xd0DD5rlcEPMI4fNX6oTywwpsC1Qb2F6dlQ5GgchEoyizkmRamXlqqaHHl rmaz1snxo4eIe2LfTK7j5t/VHh5yXCU4eLp1kbwk53AtJEwr/tSy3MuSTH0SP4FCdY3M81hwh4va/ P9al/mgEILjAaLEIu3H1R8ZpPMbAhEsIl2oGP1bWjxg23qB4tr2g4JzEbDyBlCcgrbvjLSBkqLjxo /UkgH0PcotnU6zL7FIO3IwTjEZ1ZVSu9PTD8B84m1cE9SurIzpmo3grsIMf/ydnP9el7QVOGosr4n dqnM6HBA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o8ysu-006qRf-9u; Wed, 06 Jul 2022 06:51:40 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1o8ysp-006qOi-3R for linux-nvme@lists.infradead.org; Wed, 06 Jul 2022 06:51:36 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 79E0F67373; Wed, 6 Jul 2022 08:51:27 +0200 (CEST) Date: Wed, 6 Jul 2022 08:51:27 +0200 From: Christoph Hellwig To: Logan Gunthorpe Cc: Greg Kroah-Hartman , Christoph Hellwig , Jason Gunthorpe , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Stephen Bates , Dan Williams , Christian =?iso-8859-1?Q?K=F6nig?= , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy , Martin Oliveira , Chaitanya Kulkarni , Ralph Campbell , Bjorn Helgaas Subject: Re: [PATCH v7 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem() Message-ID: <20220706065127.GA27132@lst.de> References: <20220705135102.GE23621@ziepe.ca> <20220705161240.GB13721@lst.de> <20220705164315.GB14484@lst.de> <20220705165039.GB14566@lst.de> <1bd43ef7-0403-bd25-087c-d54d5af677e4@deltatee.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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-20220705_235135_333221_6F6A4AA8 X-CRM114-Status: GOOD ( 17.12 ) 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 Tue, Jul 05, 2022 at 12:16:45PM -0600, Logan Gunthorpe wrote: > The current version does it through a char device, but that requires > creating a simple_fs and anon_inode for teardown on driver removal, plus > a bunch of hooks through the driver that exposes it (NVMe, in this case) > to set this all up. > > Christoph is suggesting a sysfs interface which could potentially avoid > the anon_inode and all of the extra hooks. It has some significant > benefits and maybe some small downsides, but I wouldn't describe it as > horrid. Yeah, I don't think is is horrible, it fits in with the resource files for the BARs, and solves a lot of problems. Greg, can you explain what would be so bad about it?