[PATCH 0/5] optimize the downtime for vfio migration

[Longpeng(Mike)]

In vfio migration resume phase, the cost would increase if the
vfio device has more unmasked vectors. We try to optimize it in
this series.

Patch 1 & 2 are simple code cleanups.
Patch 3 defers to set irqs to vfio core.
Patch 4 & 5 defer to commit the route to KVM core. 

The test VM has 128 vcpus and 8 VF (with 65 vectors enabled),
we mesure the cost of the vfio_msix_enable for each one, and
we can see the total cost can be significantly reduced.

        Origin         Apply Patch 3     Apply Patch 3/4/5   
1st     8              4                 2
2nd     15             11                2
3rd     22             18                2
4th     24             25                3
5th     36             33                2
6th     44             40                3
7th     51             47                3
8th     58             54                4
Total   258ms          232ms             21ms


Longpeng (Mike) (5):
  vfio: use helper to simplfy the failure path in vfio_msi_enable
  msix: simplfy the conditional in msix_set/unset_vector_notifiers
  vfio: defer to enable msix in migration resume phase
  kvm: irqchip: support defer to commit the route
  vfio: defer to commit kvm route in migraiton resume phase

 accel/kvm/kvm-all.c    | 10 +++--
 accel/stubs/kvm-stub.c |  3 +-
 hw/misc/ivshmem.c      |  2 +-
 hw/pci/msix.c          |  7 ++--
 hw/vfio/pci.c          | 99 ++++++++++++++++++++++++++++++++++++++------------
 hw/vfio/pci.h          |  1 +
 hw/virtio/virtio-pci.c |  2 +-
 include/sysemu/kvm.h   |  4 +-
 target/i386/kvm/kvm.c  |  2 +-
 9 files changed, 95 insertions(+), 35 deletions(-)

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1.8.3.1