From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keith Busch <keith.busch-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH v2 10/10] nvmet: Optionally use PCI P2P memory
Date: Thu, 1 Mar 2018 16:49:30 -0700
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Cc: Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>, Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, "linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org" <linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>, "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>, "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" <linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>, "linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Jason Gunthorpe <jgg-uk2M96/98Pc@public.gmane.org>, =?iso-8859-1?B?Suly9G1l?= Glisse <jglisse-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>, Bjorn Helgaas <bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Max Gurtovoy <maxg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>, Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
List-Id: linux-rdma@vger.kernel.org

On Thu, Mar 01, 2018 at 11:00:51PM +0000, Stephen  Bates wrote:
> 
> P2P is about offloading the memory and PCI subsystem of the host CPU
> and this is achieved no matter which p2p_dev is used.

Even within a device, memory attributes for its various regions may not be
the same. There's a meaningful difference between writing to an NVMe CMB
vs PMR, and a single device could have both. We don't want to lump these
all together without knowing which region you're allocating from, right?