[PATCH 0/3] virtio-net: graceful drop of vhost for TAP

[Yuri Benditovich]

This set of patches introduces graceful switch from tap-vhost to
tap-no-vhost depending on guest features. Before that the features
that vhost does not support were silently cleared in get_features.
This creates potential problem of migration from the machine where
some of virtio-net features are supported by the vhost kernel to the
machine where they are not supported (packed ring as an example).

Instead of silent masking of the features virtio-net gracefully
disables the vhost at set_features if some features acked by the
guest contradict with kernel vhost capabilities.

This set of patches also makes get_vhost_net() call (that used
everywhere) to always return actual result, i.e. initially it
returns non-NULL value and from the moment the vhost was disabled
the call will return NULL. Such a way we avoid any unexpected
calls to vhost functions.
Yuri Benditovich (3):
  vhost-net: add VIRTIO_NET_F_HASH_REPORT to the list of kernel features
  net: add ability to hide (disable) vhost_net
  virtio-net: graceful fallback to vhost=off for tap netdev

 hw/net/vhost_net.c  |  5 +++-
 hw/net/virtio-net.c | 58 ++++++++++++++++++++++++++++++++++++++-------
 include/net/net.h   |  1 +
 3 files changed, 55 insertions(+), 9 deletions(-)

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2.17.1