linux-kernel - Re: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory

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Date:   Thu, 1 Mar 2018 14:22:56 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Jerome Glisse <jglisse@...hat.com>
Cc:     benh@....ibm.com, Dan Williams <dan.j.williams@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pci@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-rdma <linux-rdma@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        linux-block@...r.kernel.org, Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Keith Busch <keith.busch@...el.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Oliver OHalloran <oliveroh@....ibm.com>
Subject: Re: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory



On 01/03/18 02:18 PM, Jerome Glisse wrote:
> This is pretty easy to do with HMM:
> 
> unsigned long hmm_page_to_phys_pfn(struct page *page)
This is not useful unless you want to go through all the kernel paths we 
are using and replace page_to_phys() and friends with something else 
that calls an HMM function when appropriate...

The problem isn't getting the physical address from a page, it's that we 
are passing these pages through various kernel interfaces which expect 
pages that work in the usual manner. (Look at the code: we quite simply 
provide a way to get the PCI bus address from a page when necessary).

Logan