virtio-net: support reset queue

A separate reset queue function introduced by Virtqueue Reset.

However, it is currently not defined what to do if the destination queue is
being reset when virtio-net is steering in multi-queue mode.

Fixes: #138

Reviewed-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

content.tex

@@ -4337,6 +4337,10 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
 \field{virtqueue_pairs} once it has placed the
 VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET command in a used buffer.
 
+If the destination receive queue is being reset (See \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset}),
+the device SHOULD re-select another random queue. If all receive queues are
+being reset, the device MUST drop the packet.
+
 \subparagraph{Legacy Interface: Automatic receive steering in multiqueue mode}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode / Legacy Interface: Automatic receive steering in multiqueue mode}
 When using the legacy interface, transitional devices and drivers
 MUST format \field{virtqueue_pairs}
@@ -4425,6 +4429,7 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
 \item Calculate the hash of the packet as defined in \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets}.
 \item If the device did not calculate the hash for the specific packet, the device directs the packet to the receiveq specified by \field{unclassified_queue} of virtio_net_rss_config structure (value of 0 corresponds to receiveq1).
 \item Apply \field{indirection_table_mask} to the calculated hash and use the result as the index in the indirection table to get 0-based number of destination receiveq (value of 0 corresponds to receiveq1).
+\item If the destination receive queue is being reset (See \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset}), the device MUST drop the packet.
 \end{itemize}
 
 \paragraph{Offloads State Configuration}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Offloads State Configuration}