From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Subject: Re: Enabling peer to peer device transactions for PCIe devices
Date: Thu, 24 Nov 2016 09:26:20 -0700
Message-ID: <20161124162620.GC20818@obsidianresearch.com>
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On Thu, Nov 24, 2016 at 10:45:18AM +0100, Christian K=F6nig wrote:
> Am 24.11.2016 um 00:25 schrieb Jason Gunthorpe:
> >There is certainly nothing about the hardware that cares
> >about ZONE_DEVICE vs System memory.
> Well that is clearly not so simple. When your ZONE_DEVICE pages describe a
> PCI BAR and another PCI device initiates a DMA to this address the DMA
> subsystem must be able to check if the interconnection really works.

I said the hardware doesn't care.. You are right, we still have an
outstanding problem in Linux of how to generically DMA map a P2P
address - which is a different issue from getting the P2P address from
a __user pointer...

Jason