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Re: [Qemu-devel] [PATCH V4 00/19] Support more virtio queues

From: Jason Wang
Subject: Re: [Qemu-devel] [PATCH V4 00/19] Support more virtio queues
Date: Thu, 19 Mar 2015 13:24:53 +0800

On Wed, Mar 18, 2015 at 8:58 PM, Michael S. Tsirkin <address@hidden> wrote:
On Wed, Mar 18, 2015 at 05:34:50PM +0800, Jason Wang wrote:
 We current limit the max virtio queues to 64. This is not sufficient
 to support multiqueue devices (e.g recent Linux support up to 256
tap queues). So this series tries to let virtio to support more queues. No much works need to be done except: - Introducing transport specific queue limitation.
 - Let each virtio transport to use specific limit.
 - Speedup the MSI-X masking and unmasking through per vector queue
   list, and increase the maximum MSI-X vectors supported by qemu.
 - With the above enhancements, increase the maximum number of
   virtqueues supported by PCI from 64 to 513.
 - Compat the changes for legacy machine types.

What are the compatibility considerations here?

Two considerations:
1) To keep msix bar size to 4K for legacy machine types
2) Limit the pci queue max to 64 for legacy machine types

 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 on other
 targets. And make check on s390x-softmmu and ppc64-softmmu.
Cc: Paolo Bonzini <address@hidden>
 Cc: Richard Henderson <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: Christian Borntraeger <address@hidden>
 Cc: Cornelia Huck <address@hidden>
 Cc: Amit Shah <address@hidden>
 Cc: address@hidden
Please review Thanks Changes from V3:
 - rebase to master and target to 2.4
 - handling compat issues for spapr
- fixes for hmp command completion when we have a nic with 256 queues
 - using VIRTIO_NO_VECTOR instead of 0 for invalid virtqueue in
 - fix compile issues for ppc64-softmmu
 - don't export VIRTIO_CCW_QUEUE_MAX by introducing a gsi limit and
   inherit in ccw
 - use transport specific queue limit in virtio-serial
- correct the stale comment for AdapterRoutes and move it to ccw patch
 - replace 128 with queue_max + 64 and add a comment for this in
Changes from V2:
 - move transport specific limitation to their implementation. (The
   left is VIRTIO_CCW_QUEUE_MAX since I fail to find a common header
   files other than virtio.h)
 - use virtio_get_queue_max() if possible in virtio.c
 - AdapterRoutes should use ccw limit
 - introduce a vector to queue mapping for virito devices and speedup
   the MSI-X masking and unmasking through this.
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
Jason Wang (19):
   pc: add 2.4 machine types
   spapr: add machine type specific instance init function
   ppc: spapr: add 2.4 machine type
   monitor: replace the magic number 255 with MAX_QUEUE_NUM
   monitor: check return value of qemu_find_net_clients_except()
virtio-ccw: using VIRTIO_NO_VECTOR instead of 0 for invalid virtqueue
   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-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: introduce vector to virtqueues mapping
   virtio: introduce virtio_queue_get_index()
   virtio-pci: speedup MSI-X masking and unmasking
   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    |  2 +-
  hw/i386/pc_piix.c              | 42 ++++++++++++++++++++---
  hw/i386/pc_q35.c               | 39 +++++++++++++++++++--
  hw/misc/ivshmem.c              |  2 +-
  hw/net/virtio-net.c            |  9 ++++-
  hw/pci/msix.c                  | 18 ++++------
hw/ppc/spapr.c | 70 +++++++++++++++++++++++++++++++++++--
  hw/s390x/s390-virtio-bus.c     |  7 ++--
  hw/s390x/s390-virtio-ccw.c     |  7 ++--
  hw/s390x/virtio-ccw.c          | 20 +++++++----
  hw/scsi/virtio-scsi.c          |  4 +--
  hw/virtio/virtio-mmio.c        |  7 ++--
hw/virtio/virtio-pci.c | 78 ++++++++++++++++++++++++++++--------------
  hw/virtio/virtio-pci.h         |  3 ++
hw/virtio/virtio.c | 75 +++++++++++++++++++++++++++++++---------
  include/hw/compat.h            | 11 ++++++
  include/hw/pci/msix.h          |  2 +-
  include/hw/s390x/s390_flic.h   |  4 ++-
  include/hw/virtio/virtio-bus.h |  2 ++
  include/hw/virtio/virtio.h     |  7 ++--
  monitor.c                      | 25 ++++++++------
  22 files changed, 339 insertions(+), 97 deletions(-)
-- 2.1.0

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