linux-kernel - Re: [PATCH v8 09/13] nvme-pci: Use PCI p2pmem subsystem to manage the CMB

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Date:   Thu, 27 Sep 2018 11:10:13 -0600
From:   Keith Busch <keith.busch@...ux.intel.com>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-block@...r.kernel.org,
        Jens Axboe <axboe@...nel.dk>,
        Christian König <christian.koenig@....com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v8 09/13] nvme-pci: Use PCI p2pmem subsystem to manage
 the CMB

On Thu, Sep 27, 2018 at 10:54:16AM -0600, Logan Gunthorpe wrote:
> Register the CMB buffer as p2pmem and use the appropriate allocation
> functions to create and destroy the IO submission queues.
> 
> If the CMB supports WDS and RDS, publish it for use as P2P memory
> by other devices.
> 
> Kernels without CONFIG_PCI_P2PDMA will also no longer support NVMe CMB.
> However, seeing the main use-cases for the CMB is P2P operations,
> this seems like a reasonable dependency.
> 
> We drop the __iomem safety on the buffer seeing that, by convention, it's
> safe to directly access memory mapped by memremap()/devm_memremap_pages().
> Architectures where this is not safe will not be supported by memremap()
> and therefore will not be support PCI P2P and have no support for CMB.
> 
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>

Looks good to me.

Reviewed-by: Keith Busch <keith.busch@...el.com>