We can't always support mmap across an entire device region, for
example we deny mmaps covering the MSI-X table of PCI devices, but
we don't really have a way to report it. We expect the user to
implicitly know this restriction. We also can't split the region
because vfio-pci defines an API with fixed region index to BAR
number mapping. We therefore define a new capability which lists
areas within the region that may be mmap'd. In addition to the
MSI-X case, this potentially enables in-kernel emulation and
extensions to devices.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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