• Dan Williams's avatar
    kvm: rename pfn_t to kvm_pfn_t · ba049e93
    Dan Williams authored
    To date, we have implemented two I/O usage models for persistent memory,
    PMEM (a persistent "ram disk") and DAX (mmap persistent memory into
    userspace).  This series adds a third, DAX-GUP, that allows DAX mappings
    to be the target of direct-i/o.  It allows userspace to coordinate
    DMA/RDMA from/to persistent memory.
    The implementation leverages the ZONE_DEVICE mm-zone that went into
    4.3-rc1 (also discussed at kernel summit) to flag pages that are owned
    and dynamically mapped by a device driver.  The pmem driver, after
    mapping a persistent memory range into the system memmap via
    devm_memremap_pages(), arranges for DAX to distinguish pfn-only versus
    page-backed pmem-pfns via flags in the new pfn_t type.
    The DAX code, upon seeing a PFN_DEV+PFN_MAP flagged pfn, flags the
    resulting pte(s) inserted into the process page tables with a new
    _PAGE_DEVMAP flag.  Later, when get_user_pages() is walking ptes it keys
    off _PAGE_DEVMAP to pin the device hosting the page range active.
    Finally, get_page() and put_page() are modified to take references
    against the device driver established page mapping.
    Finally, this need for "struct page" for persistent memory requires
    memory capacity to store the memmap array.  Given the memmap array for a
    large pool of persistent may exhaust available DRAM introduce a
    mechanism to allocate the memmap from persistent memory.  The new
    "struct vmem_altmap *" parameter to devm_memremap_pages() enables
    arch_add_memory() to use reserved pmem capacity rather than the page
    This patch (of 18):
    The core has developed a need for a "pfn_t" type [1].  Move the existing
    pfn_t in KVM to kvm_pfn_t [2].
    [1]: https://lists.01.org/pipermail/linux-nvdimm/2015-September/002199.html
    [2]: https://lists.01.org/pipermail/linux-nvdimm/2015-September/002218.htmlSigned-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    Acked-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
kvm_types.h 1.59 KB