[Qemu-devel] [PATCH v2 0/2] virtio: Move host features to backends

[shannon . zhao]

From: Shannon Zhao <address@hidden>

The reason to do this is that the virtio-net-device can't expose host
features to guest while using virtio-mmio. So the performance is low.

The virtio-*-pci, virtio-*-s390, and virtio-*-ccw already have the ability
to forward property accesses to the backend child, by calling 
*_virtio_*_instance_init -> qdev_alias_all_properties. So if we move the
host features to backends, it doesn't break the backwards compatibility
for virtio-*-pci, virtio-*-s390, and virtio-*-ccw.

Here we move the host features to backends, involving
DEFINE_VIRTIO_NET_FEATURES, DEFINE_VIRTIO_SCSI_FEATURES. So the virtio-mmio
devices could have the host freatures, and this has a great performance
improvement to virtio-mmio, especially to virtio-net-device.

changes since v1:
  * drop unnecessary change of adding device_plugged hook for
    virtio-ccw and s390-virtio-bus (Cornelia)

Shannon Zhao (2):
  hw/net/virtio-net: Move DEFINE_VIRTIO_NET_FEATURES to virtio-net
  virtio-scsi: Move DEFINE_VIRTIO_SCSI_FEATURES to virtio-scsi

 hw/net/virtio-net.c             | 4 ++++
 hw/s390x/s390-virtio-bus.c      | 2 --
 hw/s390x/virtio-ccw.c           | 2 --
 hw/scsi/virtio-scsi.c           | 5 +++++
 hw/virtio/virtio-pci.c          | 2 --
 include/hw/virtio/virtio-net.h  | 1 +
 include/hw/virtio/virtio-scsi.h | 1 +
 7 files changed, 11 insertions(+), 6 deletions(-)

-- 
2.0.4