[v4,0/6] optimize the downtime for vfio migration

Message

Longpeng(Mike) Oct. 14, 2021, 12:48 a.m. UTC

Hi guys,
 
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.
 
You can see the commit message in PATCH 6 for details.
 
Patch 1-3 are simple cleanups and fixup.
Patch 4-5 are the preparations for the optimization.
Patch 6 optimizes the vfio msix setup path.

Changes v3->v4:
 - fix several typos and grammatical errors [Alex]
 - remove the patches that fix and clean the MSIX common part
   from this series [Alex]
 - Patch 6:
    - use vector->use directly and fill it with -1 on error
      paths [Alex]
    - add comment before enable deferring to commit [Alex]
    - move the code that do_use/release on vector 0 into an
      "else" branch [Alex]
    - introduce vfio_prepare_kvm_msi_virq_batch() that enables
      the 'defer_kvm_irq_routing' flag [Alex]
    - introduce vfio_commit_kvm_msi_virq_batch() that clears the
      'defer_kvm_irq_routing' flag and does further work [Alex]

Changes v2->v3:
 - fix two errors [Longpeng]

Changes v1->v2:
 - fix several typos and grammatical errors [Alex, Philippe]
 - split fixups and cleanups into separate patches  [Alex, Philippe]
 - introduce kvm_irqchip_add_deferred_msi_route to
   minimize code changes    [Alex]
 - enable the optimization in msi setup path    [Alex]

Longpeng (Mike) (6):
  vfio: simplify the conditional statements in vfio_msi_enable
  vfio: move re-enabling INTX out of the common helper
  vfio: simplify the failure path in vfio_msi_enable
  kvm: irqchip: extract kvm_irqchip_add_deferred_msi_route
  Revert "vfio: Avoid disabling and enabling vectors repeatedly in VFIO
    migration"
  vfio: defer to commit kvm irq routing when enable msi/msix

 accel/kvm/kvm-all.c  |  15 ++++-
 hw/vfio/pci.c        | 182 +++++++++++++++++++++++++++++++++------------------
 hw/vfio/pci.h        |   1 +
 include/sysemu/kvm.h |   6 ++
 4 files changed, 140 insertions(+), 64 deletions(-)