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    SubjectRe: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory
    On Wed, Feb 28, 2018 at 7:56 PM, Benjamin Herrenschmidt
    <benh@au1.ibm.com> wrote:
    > On Thu, 2018-03-01 at 14:54 +1100, Benjamin Herrenschmidt wrote:
    >> On Wed, 2018-02-28 at 16:39 -0700, Logan Gunthorpe wrote:
    >> > Hi Everyone,
    >>
    >>
    >> So Oliver (CC) was having issues getting any of that to work for us.
    >>
    >> The problem is that acccording to him (I didn't double check the latest
    >> patches) you effectively hotplug the PCIe memory into the system when
    >> creating struct pages.
    >>
    >> This cannot possibly work for us. First we cannot map PCIe memory as
    >> cachable. (Note that doing so is a bad idea if you are behind a PLX
    >> switch anyway since you'd ahve to manage cache coherency in SW).
    >
    > Note: I think the above means it won't work behind a switch on x86
    > either, will it ?

    The devm_memremap_pages() infrastructure allows placing the memmap in
    "System-RAM" even if the hotplugged range is in PCI space. So, even if
    it is an issue on some configurations, it's just a simple adjustment
    to where the memmap is placed.

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