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    SubjectRe: [patch 0/6] MMU Notifiers V6
    On Fri, 08 Feb 2008 14:06:16 -0800
    Christoph Lameter <clameter@sgi.com> wrote:

    > This is a patchset implementing MMU notifier callbacks based on Andrea's
    > earlier work. These are needed if Linux pages are referenced from something
    > else than tracked by the rmaps of the kernel (an external MMU). MMU
    > notifiers allow us to get rid of the page pinning for RDMA and various
    > other purposes. It gets rid of the broken use of mlock for page pinning.
    > (mlock really does *not* pin pages....)
    >
    > More information on the rationale and the technical details can be found in
    > the first patch and the README provided by that patch in
    > Documentation/mmu_notifiers.
    >
    > The known immediate users are
    >
    > KVM
    > - Establishes a refcount to the page via get_user_pages().
    > - External references are called spte.
    > - Has page tables to track pages whose refcount was elevated but
    > no reverse maps.
    >
    > GRU
    > - Simple additional hardware TLB (possibly covering multiple instances of
    > Linux)
    > - Needs TLB shootdown when the VM unmaps pages.
    > - Determines page address via follow_page (from interrupt context) but can
    > fall back to get_user_pages().
    > - No page reference possible since no page status is kept..
    >
    > XPmem
    > - Allows use of a processes memory by remote instances of Linux.
    > - Provides its own reverse mappings to track remote pte.
    > - Established refcounts on the exported pages.
    > - Must sleep in order to wait for remote acks of ptes that are being
    > cleared.
    >

    What about ib_umem_get()?


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