vfio/type1: Improve memory pinning process for raw PFN mapping

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When using vfio to pass through a PCIe device (e.g. a GPU card) that
has a huge BAR (e.g. 16GB), a lot of cycles are wasted on memory
pinning because PFNs of PCI BAR are not backed by struct page, and
the corresponding VMA has flag VM_PFNMAP.

With this change, when pinning a region which is a raw PFN mapping,
it can skip unnecessary user memory pinning process, and thus, can
significantly improve VM's boot up time when passing through devices
via VFIO. In my test on a Xeon E5 2.6GHz, the time mapping a 16GB
BAR was reduced from about 0.4s to 1.5us.

Signed-off-by: Jason Cai (Xiang Feng) <jason.cai@linux.alibaba.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

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Jason Cai (Xiang Feng) 2018-03-22 12:52:16 +08:00 • committed by Alex Williamson

parent c9f89c3f87

commit 356e88ebe4

1 changed files with 15 additions and 10 deletions

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drivers/vfio/vfio_iommu_type1.c

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