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From: Dan Williams <dan.j.williams@intel.com>
Date: Wed, 26 Oct 2016 06:39:05 -0700
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Subject: Re: [PATCH 0/3] iopmem : A block device for PCIe memory
To: Haggai Eran <haggaie@mellanox.com>
Cc: Stephen Bates <sbates@raithlin.com>,
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        Linux MM <linux-mm@kvack.org>,
        Ross Zwisler <ross.zwisler@linux.intel.com>,
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        Christoph Hellwig <hch@infradead.org>, Jens Axboe <axboe@fb.com>,
        Jonathan Corbet <corbet@lwn.net>, jim.macdonald@everspin.com,
        sbates@raithin.com, Logan Gunthorpe <logang@deltatee.com>,
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        "Raj, Ashok" <ashok.raj@intel.com>
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On Wed, Oct 26, 2016 at 1:24 AM, Haggai Eran <haggaie@mellanox.com> wrote:
[..]
>> I wonder if we could (ab)use a
>> software-defined 'pasid' as the requester id for a peer-to-peer
>> mapping that needs address translation.
> Why would you need that? Isn't it enough to map the peer-to-peer
> addresses correctly in the iommu driver?
>

You're right, we might already have enough...

We would just need to audit iommu drivers to undo any assumptions that
the page being mapped is always in host memory and apply any bus
address translations between source device and target device.