The vector_use callback is used to enable vector that is unmasked in
guest. The kernel used to only support static MSI-X allocation. When
allocating a new interrupt using "static MSI-X allocation" kernels,
QEMU first disables all previously allocated vectors and then
re-allocates all including the new one. The nr_vectors of VFIOPCIDevice
indicates that all vectors from 0 to nr_vectors are allocated (and may
be enabled), which is used to loop all the possibly used vectors when
e.g., disabling MSI-X interrupts.
Extend the vector_use function to support dynamic MSI-X allocation when
host supports the capability. QEMU therefore can individually allocate
and enable a new interrupt without affecting others or causing interrupts
lost during runtime.
Utilize nr_vectors to calculate the upper bound of enabled vectors in
dynamic MSI-X allocation mode since looping all msix_entries_nr is not
efficient and unnecessary.
Signed-off-by: Jing Liu <jing2.liu@intel.com>
Tested-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
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