vhost-user: Add reconnect support

QEMU 2.7 introduces reconnect support. However it doesn't send
last state of last_avail_idx in the SET_VRING_BASE.

With this patch we are overriding SET_VRING_BASE with value taken
from used->idx.

It is a bit hackish as it basically overrides SET_VRING_BASE
provided value but it should work in most of the cases.
This is what author of reconnect code is also suggesting in his post:

https://lists.gnu.org/archive/html/qemu-devel/2016-06/msg01495.html

Change-Id: I10e5f401c409d2989bf6c43eaea377800a9c76df
Signed-off-by: Damjan Marion <damarion@cisco.com>

diff --git a/vnet/vnet/devices/virtio/vhost-user.c b/vnet/vnet/devices/virtio/vhost-user.c
index 9b0db74..a3dacd1 100644 (file)
--- a/vnet/vnet/devices/virtio/vhost-user.c
+++ b/vnet/vnet/devices/virtio/vhost-user.c
@@ -588,6 +588,7 @@ vhost_user_socket_read (unix_file_t * uf)
        }
 
       vui->vrings[msg.state.index].last_used_idx =
+       vui->vrings[msg.state.index].last_avail_idx =
        vui->vrings[msg.state.index].used->idx;
 
       /* tell driver that we don't want interrupts */