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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,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 0100CC55ABD for ; Mon, 9 Nov 2020 16:50:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5EF5B221E9 for ; Mon, 9 Nov 2020 16:50:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=deltatee.com header.i=@deltatee.com header.b="ThtDTaP+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5EF5B221E9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=deltatee.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A76AA6B0036; Mon, 9 Nov 2020 11:50:16 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9FF956B005D; Mon, 9 Nov 2020 11:50:16 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8C6646B006C; Mon, 9 Nov 2020 11:50:16 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0081.hostedemail.com [216.40.44.81]) by kanga.kvack.org (Postfix) with ESMTP id 570AE6B0036 for ; Mon, 9 Nov 2020 11:50:16 -0500 (EST) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 014E9180AD81A for ; Mon, 9 Nov 2020 16:50:15 +0000 (UTC) X-FDA: 77465467632.14.name26_030d4fe272ee Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin14.hostedemail.com (Postfix) with ESMTP id CDE171822987A for ; Mon, 9 Nov 2020 16:50:15 +0000 (UTC) X-HE-Tag: name26_030d4fe272ee X-Filterd-Recvd-Size: 4334 Received: from ale.deltatee.com (ale.deltatee.com [204.191.154.188]) by imf06.hostedemail.com (Postfix) with ESMTP for ; Mon, 9 Nov 2020 16:50:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=deltatee.com; s=20200525; h=Subject:Content-Transfer-Encoding:Content-Type: In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To:Sender: Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender :Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=JvTSJOBJXMYeKQM3WvNBTHeii6rtMfOVYOuXeE1KNJE=; b=ThtDTaP+0JSTSqxTpv0Wbo5rpZ iRui8AXvdDo2GGy2jD+Ihq9bjJnDiDzsI2eDLeMfjQgtCqgG1tvLOdsfhRmNEUO5jfT5M0MI5pI2v q2scQ0uSLY0gF95SrT5uiioU6950uU8eKRlO3IC5Z9K0t/8xAxKw/BHncD9WkCSO21vni9bfdfdjX Ln7KngxHrH+R5I2NkjQEaqpyQ8667dJ8gO+usI96NSRpENPnyhncaujMAMnPoIfhN4BFg8hdAnZFw mUlKnwOWo6dpdcffw7/1fMcc6qlFJ5qgEkOsQqBOUl2OSNvLl4XkpF9pd5ChHmt9ndYzbgPOuwY5t OGbul4GA==; Received: from guinness.priv.deltatee.com ([172.16.1.162]) by ale.deltatee.com with esmtp (Exim 4.92) (envelope-from ) id 1kcAMk-00013k-Ea; Mon, 09 Nov 2020 09:50:03 -0700 To: Keith Busch Cc: 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 , Christoph Hellwig , Dan Williams , Jason Gunthorpe , =?UTF-8?Q?Christian_K=c3=b6nig?= , Ira Weiny , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter References: <20201106170036.18713-1-logang@deltatee.com> <20201106170036.18713-16-logang@deltatee.com> <20201109150326.GA2221592@dhcp-10-100-145-180.wdc.com> From: Logan Gunthorpe Message-ID: Date: Mon, 9 Nov 2020 09:50:00 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <20201109150326.GA2221592@dhcp-10-100-145-180.wdc.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: daniel.vetter@ffwll.ch, willy@infradead.org, ddutile@redhat.com, jhubbard@nvidia.com, iweiny@intel.com, christian.koenig@amd.com, jgg@ziepe.ca, dan.j.williams@intel.com, hch@lst.de, sbates@raithlin.com, iommu@lists.linux-foundation.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, kbusch@kernel.org X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [RFC PATCH 15/15] nvme-pci: Allow mmaping the CMB in userspace X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) 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: On 2020-11-09 8:03 a.m., Keith Busch wrote: > On Fri, Nov 06, 2020 at 10:00:36AM -0700, Logan Gunthorpe wrote: >> Allow userspace to obtain CMB memory by mmaping the controller's >> char device. The mmap call allocates and returns a hunk of CMB memory, >> (the offset is ignored) so userspace does not have control over the >> address within the CMB. >> >> A VMA allocated in this way will only be usable by drivers that set >> FOLL_PCI_P2PDMA when calling GUP. And inter-device support will be >> checked the first time the pages are mapped for DMA. >> >> Currently this is only supported by O_DIRECT to an PCI NVMe device >> or through the NVMe passthrough IOCTL. > > Rather than make this be specific to nvme, could pci p2pdma create an > mmap'able file for any resource registered with it? It's certainly possible. However, other people have been arguing that more of this should be specific to NVMe as some use cases do not want to use the genalloc inside p2pdma. Logan