[Qemu-devel] removing on-demand msix vector allocation

["Michael S. Tsirkin" <mst@redhat.com>]

I've been looking at handling of msix masking
in qemu. It looks like all of virtio,vfio and
device assignment implemented their own
similar but slightly different thing.
So I am inclined to move this handling to common
code in msix.c, adding irqfd support right there.

While doing this rework, one of the more painful
bits of code to change is the code that dynamically
allocates msix table entries as we inject msi.
If this actually triggers it's going to be
painfully slow as route changes are rcu
write side in kernel.
Since recent kernels support direct injection,
do we care anymore? I think if you run out of
vectors, it's better to simply disable irqchip
than try to limp along changing routes all the time.

Comments?

-- 
MST