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Date:   Fri, 24 May 2019 16:12:15 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     "Koenig, Christian" <Christian.Koenig@amd.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Logan Gunthorpe <logang@deltatee.com>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH] PCI/P2PDMA: Root complex whitelist should not apply
 when an IOMMU is present
Message-ID: <20190524141215.GB23514@lst.de>
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On Fri, May 24, 2019 at 12:40:57PM +0000, Koenig, Christian wrote:
> Sounds sane to me as well.
> 
> But since I don't have a struct pages backing my PCI BAR I won't be able 
> to use pci_p2pdma_map_sg.
> 
> How should we work around that?

I think we've got two escalation levels here:

 (1) fix the NVMe/RDMA p2p breakage for 5.2-rc - for that we just need
     the above fix in the p2p map_sg routine (and add an unmap_sg
     routine there)
 (2) figure out how to handle the switched case for your code.  I'm not
     sure about that yet, and without a struct page we'd have to somehow
     track the relationship explicitly.