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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 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-Language: en-CA 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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201109_115015_244340_2B107292 X-CRM114-Status: GOOD ( 14.24 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Matthew Wilcox , Jason Gunthorpe , linux-pci@vger.kernel.org, Daniel Vetter , Ira Weiny , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Stephen Bates , linux-block@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Don Dutile , =?UTF-8?Q?Christian_K=c3=b6nig?= , John Hubbard , Dan Williams , Christoph Hellwig Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org 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 _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme