tuntap: RCUify dereferencing between tun_struct and tun_file

Signed-off-by: Jason Wang <jasowang@redhat.com>
tuntap: introduce multiqueue flags

Add flags to be used by creating multiqueue tuntap device.

Signed-off-by: Jason Wang <jasowang@redhat.com>
tuntap: multiqueue support

This patch converts tun/tap to a multiqueue devices and expose the multiqueue
queues as multiple file descriptors to userspace.Internally, an array of
pointers to tun_file were introduced in the device, so multiple tun_tfiles were
allowed to be attached to the device as multiple queues. To synchronize the
control path with data path, RCU is used to protected the references from both
sides - tun_file and tun_struct.

As we could have multiple sockets now, so the limit number of packets per socket
were set to by diviging the tx queue length by the number of queues.

Tx queue selecting were based the rx hash of the packet to make sure a flow have
a consistent queue to be transmitted. In the future, more policys may be added.

Signed-off-by: Jason Wang <jasowang@redhat.com>
tuntap: add ioctl to attach or detach a file form tuntap device

Sometimes usespace may need to active/deactive a queue, this could be done by
detaching and attaching a file from tuntap device.

This patch introduces a new ioctls - TUNSETQUEUE which could be used to do
this. Flag IFF_ATTACH_QUEUE were introduced to do attaching while
IFF_DETACH_QUEUE were introduced to do the detaching.

Signed-off-by: Jason Wang <jasowang@redhat.com>
virtio_net: Introduce VIRTIO_NET_F_MULTIQUEUE

Introduce VIRTIO_NET_F_MULTIQUEUE.

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
virtio_ring: move queue_index to vring_virtqueue

Instead of storing the queue index in virtio infos, this patch moves them to
vring_virtqueue and introduces helpers to set and get the value. This would
simplify the management and tracing.

Signed-off-by: Jason Wang <jasowang@redhat.com>
virtio: intorduce an API to set affinity for a virtqueue

Sometimes, virtio device need to configure irq affiniry hint to maximize the
performance. Instead of just exposing the irq of a virtqueue, this patch
introduce an API to set the affinity for a virtqueue.

The api is best-effort, the affinity hint may not be set as expected due to
platform support, irq sharing or irq type. Currently, only pci method were
implemented and we set the affinity according to:

- if device uses INTX, we just ignore the request
- if device has per vq vector, we force the affinity hint
- if the virtqueues share MSI, make the affinity OR over all affinities
 requested

Signed-off-by: Jason Wang <jasowang@redhat.com>
virtio_net: multiqueue support

This addes multiqueue support to virtio_net driver. This feature is negotiated
through VIRTIO_NET_F_MULTIQUEUE.

The driver expects the number of rx/tx queue paris is equal to the number of
vcpus. To maximize the performance under this per-cpu rx/tx queue pairs, some
optimization were introduced:

- Txq selection is based on the processor id in order to avoid contending a lock
 whose owner may exits to host.
- Since the txq/txq were per-cpu, affinity hint were set to the cpu that owns
 the queue pairs.

This aslo patch let the virtio_net driver can negotiate the number of queues it
wishes to use through control virtqueue and export an ethtool interface to let
use tweak it.

As current multiqueue virtio-net implementation has optimizations on per-cpu
virtuqueues, so only two modes were support:

- single queue pair mode
- multiple queue paris mode, the number of queues matches the number of vcpus

The single queue mode were used by default currently due to regression of
multiqueue mode in some test (especially in stream test).

Since virtio core does not support paritially deleting virtqueues, so during
mode switching the whole virtqueue were deleted and the driver would re-create
the virtqueues it would used.

btw. The queue number negotiating were defered to .ndo_open(), this is because
only after feature negotitaion could we send the command to control virtqueue
(as it may also use event index).

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>