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[207.54.116.67]) by mx.google.com with ESMTPS id j82si613532itb.63.2019.01.29.12.40.00 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 29 Jan 2019 12:40:01 -0800 (PST) Received-SPF: pass (google.com: domain of logang@deltatee.com designates 207.54.116.67 as permitted sender) client-ip=207.54.116.67; Authentication-Results: mx.google.com; spf=pass (google.com: domain of logang@deltatee.com designates 207.54.116.67 as permitted sender) smtp.mailfrom=logang@deltatee.com Received: from guinness.priv.deltatee.com ([172.16.1.162]) by ale.deltatee.com with esmtp (Exim 4.89) (envelope-from ) id 1goaAh-0006hr-4u; Tue, 29 Jan 2019 13:39:51 -0700 To: Jason Gunthorpe , Jerome Glisse Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Greg Kroah-Hartman , "Rafael J . Wysocki" , Bjorn Helgaas , Christian Koenig , Felix Kuehling , "linux-pci@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Joerg Roedel , "iommu@lists.linux-foundation.org" References: <20190129174728.6430-1-jglisse@redhat.com> <20190129174728.6430-4-jglisse@redhat.com> <20190129191120.GE3176@redhat.com> <20190129193250.GK10108@mellanox.com> From: Logan Gunthorpe Message-ID: <99c228c6-ef96-7594-cb43-78931966c75d@deltatee.com> Date: Tue, 29 Jan 2019 13:39:49 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190129193250.GK10108@mellanox.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: iommu@lists.linux-foundation.org, jroedel@suse.de, robin.murphy@arm.com, m.szyprowski@samsung.com, hch@lst.de, dri-devel@lists.freedesktop.org, linux-pci@vger.kernel.org, Felix.Kuehling@amd.com, christian.koenig@amd.com, bhelgaas@google.com, rafael@kernel.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, jglisse@redhat.com, jgg@mellanox.com X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [RFC PATCH 3/5] mm/vma: add support for peer to peer to device vma X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +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 2019-01-29 12:32 p.m., Jason Gunthorpe wrote: > Jerome, I think it would be nice to have a helper scheme - I think the > simple case would be simple remapping of PCI BAR memory, so if we > could have, say something like: > > static const struct vm_operations_struct my_ops { > .p2p_map = p2p_ioremap_map_op, > .p2p_unmap = p2p_ioremap_unmap_op, > } > > struct ioremap_data { > [..] > } > > fops_mmap() { > vma->private_data = &driver_priv->ioremap_data; > return p2p_ioremap_device_memory(vma, exporting_device, [..]); > } This is roughly what I was expecting, except I don't see exactly what the p2p_map and p2p_unmap callbacks are for. The importing driver should see p2pdma/hmm struct pages and use the appropriate function to map them. It shouldn't be the responsibility of the exporting driver to implement the mapping. And I don't think we should have 'special' vma's for this (though we may need something to ensure we don't get mapping requests mixed with different types of pages...). I also figured there'd be a fault version of p2p_ioremap_device_memory() for when you are mapping P2P memory and you want to assign the pages lazily. Though, this can come later when someone wants to implement that. Logan