[Qemu-devel] [PATCH V2 00/11] Support more virtio queues

[Jason Wang]

We current limit the max virtio queues to 64. This is not sufficient
to support some multiqueue deivces (e.g recent Linux support up to 256
tap queues). So this series try to let virtio to support more queues.

No much works needs to be done except:

- Patch 1 add a check to validate the queues supported by backend
  against the virtio queue limitation
- Patch 2 fixes a bug in virtio_del_queue()
- Patch 3 introdues a bus specific queue limitation
- Patch 4 - Patch 8 let each transport to use bus specific queue
  limitation instead of VIRTIO_PCI_QUEUE_MAX
- Patch 9 increase the maximum number of queues supported by
  virtio-pci from 64 to 513, and deal with the migration compatibility
  with the changes.
- Patch 10 tries to remove the hard coded MSI-X bar size (4096) and
  allow up to 2048 MSI-X entries.
- Patch 11 add a boolean property to let the virtio-net can calculate
  the MSI-X bar size based on the number of MSI-X vectors and keep
  migration compatibility with legacy version whose bar size is 4096.

With this patch, we can support up to 256 queues. Since x86 can only
allow about 240 interrupt vectors for MSI-X, current Linux driver can
only have about 80 queue pairs has their private MSI-X interrupt
vectors. With sharing IRQ with queue pairs (RFC posted in
https://lkml.org/lkml/2014/12/25/169), Linux driver can have up
to about 186 queue pairs has their private MSI-X interrupt vectors.

Stress/migration test on virtio-pci, compile test/make check on other
s390-softmmu.

Cc: Paolo Bonzini <address@hidden>
Cc: Richard Henderson <address@hidden>
Cc: Anthony Liguori <address@hidden>
Cc: Michael S. Tsirkin <address@hidden>
Cc: Alexander Graf <address@hidden>
Cc: Keith Busch <address@hidden>
Cc: Kevin Wolf <address@hidden>
Cc: Stefan Hajnoczi <address@hidden>
Cc: Anthony Liguori <address@hidden>
Cc: Christian Borntraeger <address@hidden>
Cc: Cornelia Huck <address@hidden>
Cc: Amit Shah <address@hidden>

Please review

Thanks

Changes from V1:
- add a validation against the bus limitation
- switch to use a bus specific queue limit instead of a global one,
  this will allow us to just increase the limit of one transport
  without disturbing others.
- only increase the queue limit of virtio-pci
- limit the maximum number of virtio queues to 64 for legacy machine
  types

Jason Wang (11):
  virtio-net: validate backend queue numbers against bus limitation
  virtio-net: fix the upper bound when trying to delete queues
  virito: introduce bus specific queue limit
  virtio-ccw: introduce ccw specific queue limit
  virtio-serial-bus: switch to bus specific queue limit
  virtio-s390: switch to bus specific queue limit
  virtio-mmio: switch to bus specific queue limit
  virtio-pci: switch to use bus specific queue limit
  virtio-pci: increase the maximum number of virtqueues to 513
  pci: remove hard-coded bar size in msix_init_exclusive_bar()
  virtio-pci: introduce auto_msix_bar_size property

 hw/block/nvme.c                |  2 +-
 hw/char/virtio-serial-bus.c    |  4 +++-
 hw/i386/pc_piix.c              | 10 ++++++++
 hw/i386/pc_q35.c               |  9 ++++++++
 hw/misc/ivshmem.c              |  2 +-
 hw/net/virtio-net.c            |  9 +++++++-
 hw/pci/msix.c                  | 18 ++++++---------
 hw/ppc/spapr.c                 |  5 ++++
 hw/s390x/s390-virtio-bus.c     |  5 ++--
 hw/s390x/s390-virtio-ccw.c     |  7 ++++--
 hw/s390x/virtio-ccw.c          | 12 ++++++----
 hw/scsi/virtio-scsi.c          |  4 ++--
 hw/virtio/virtio-mmio.c        |  5 ++--
 hw/virtio/virtio-pci.c         | 28 +++++++++++++++++------
 hw/virtio/virtio-pci.h         |  3 +++
 hw/virtio/virtio.c             | 52 +++++++++++++++++++++++++++++++-----------
 include/hw/compat.h            |  8 +++++++
 include/hw/pci/msix.h          |  2 +-
 include/hw/s390x/s390_flic.h   |  2 +-
 include/hw/virtio/virtio-bus.h |  1 +
 include/hw/virtio/virtio.h     |  6 ++++-
 21 files changed, 143 insertions(+), 51 deletions(-)

-- 
1.9.1