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From:   Logan Gunthorpe <logang@deltatee.com>
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Date:   Mon, 26 Mar 2018 14:42:05 -0600
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Subject: Re: [PATCH v3 01/11] PCI/P2PDMA: Support peer-to-peer memory
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On 26/03/18 01:35 PM, Jason Gunthorpe wrote:
> I think this is another case of the HW can do it but the SW support is
> missing. IOMMU configuration and maybe firmware too, for instance.

Nope, not sure how you can make this leap. We've been specifically told
that peer-to-peer PCIe DMA is not supported on P9. We've also been told
there is a very limited (ie. store only), low performance mode designed
for poking mailboxes but it is disabled by default and must be enable
with some kind of special firmware calls.

Logan