Re: [Qemu-devel] [PATCH v4 0/2] virtio: Move host features to backends

[Michael S. Tsirkin]

On Tue, Apr 28, 2015 at 07:51:11PM +0800, address@hidden wrote:
> 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.

Can you move COMMON_FEATURES too please?

> changes since v3:
>   * detail the changes in commit log
>   * don't expose virtio_net_set_config_size
> 
> changes since v2:
>   * move virtio_net_set_config_size to virtio-net (Cornelia)
> 
> changes since v1:
>   * drop unnecessary change of adding device_plugged hook for
>     virtio-ccw and s390-virtio-bus (Cornelia)
> 
> Shannon Zhao (2):
>   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             | 7 ++++++-
>  hw/s390x/s390-virtio-bus.c      | 3 ---
>  hw/s390x/virtio-ccw.c           | 3 ---
>  hw/scsi/virtio-scsi.c           | 5 +++++
>  hw/virtio/virtio-pci.c          | 3 ---
>  include/hw/virtio/virtio-net.h  | 2 +-
>  include/hw/virtio/virtio-scsi.h | 1 +
>  7 files changed, 13 insertions(+), 11 deletions(-)
> 
> -- 
> 2.1.0