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| author | Alexey Kardashevskiy <aik@ozlabs.ru> | 2018-03-13 11:17:31 -0600 |
|---|---|---|
| committer | Alex Williamson <alex.williamson@redhat.com> | 2018-03-13 11:17:31 -0600 |
| commit | ae0215b2bb56a9d5321a185dde133bfdd306a4c0 (patch) | |
| tree | f1c9b9a0e00f478aabaeb163dcf42e9c41a908f5 /qapi/block.json | |
| parent | 567b5b309abe744b1098018a2eb157e7109c9f30 (diff) | |
vfio-pci: Allow mmap of MSIX BAR
At the moment we unconditionally avoid mapping MSIX data of a BAR and
emulate MSIX table in QEMU. However it is 1) not always necessary as
a platform may provide a paravirt interface for MSIX configuration;
2) can affect the speed of MMIO access by emulating them in QEMU when
frequently accessed registers share same system page with MSIX data,
this is particularly a problem for systems with the page size bigger
than 4KB.
A new capability - VFIO_REGION_INFO_CAP_MSIX_MAPPABLE - has been added
to the kernel [1] which tells the userspace that mapping of the MSIX data
is possible now. This makes use of it so from now on QEMU tries mapping
the entire BAR as a whole and emulate MSIX on top of that.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a32295c612c57990d17fb0f41e7134394b2f35f6
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Diffstat (limited to 'qapi/block.json')
0 files changed, 0 insertions, 0 deletions