diff options
Diffstat (limited to 'doc/guides/nics/virtio.rst')
| -rw-r--r-- | doc/guides/nics/virtio.rst | 75 |
1 files changed, 69 insertions, 6 deletions
diff --git a/doc/guides/nics/virtio.rst b/doc/guides/nics/virtio.rst index 06ca433a..c6335d40 100644 --- a/doc/guides/nics/virtio.rst +++ b/doc/guides/nics/virtio.rst @@ -73,7 +73,7 @@ In this release, the virtio PMD driver provides the basic functionality of packe * It supports multicast packets and promiscuous mode. -* The descriptor number for the RX/TX queue is hard-coded to be 256 by qemu. +* The descriptor number for the Rx/Tx queue is hard-coded to be 256 by qemu. If given a different descriptor number by the upper application, the virtio PMD generates a warning and fall back to the hard-coded value. @@ -163,8 +163,9 @@ Host2VM communication example which means received packets come from vEth0, and transmitted packets is sent to vEth0. #. In the guest, bind the virtio device to the uio_pci_generic kernel module and start the forwarding application. - When the virtio port in guest bursts rx, it is getting packets from the raw socket's receive queue. - When the virtio port bursts tx, it is sending packet to the tx_q. + When the virtio port in guest bursts Rx, it is getting packets from the + raw socket's receive queue. + When the virtio port bursts Tx, it is sending packet to the tx_q. .. code-block:: console @@ -183,7 +184,9 @@ Host2VM communication example The packet reception and transmission flow path is: - IXIA packet generator->82599 PF->KNI rx queue->KNI raw socket queue->Guest VM virtio port 0 rx burst->Guest VM virtio port 0 tx burst-> KNI tx queue->82599 PF-> IXIA packet generator + IXIA packet generator->82599 PF->KNI Rx queue->KNI raw socket queue->Guest + VM virtio port 0 Rx burst->Guest VM virtio port 0 Tx burst-> KNI Tx queue + ->82599 PF-> IXIA packet generator Virtio with qemu virtio Back End -------------------------------- @@ -206,8 +209,68 @@ Virtio with qemu virtio Back End In this example, the packet reception flow path is: - IXIA packet generator->82599 PF->Linux Bridge->TAP0's socket queue-> Guest VM virtio port 0 rx burst-> Guest VM 82599 VF port1 tx burst-> IXIA packet generator + IXIA packet generator->82599 PF->Linux Bridge->TAP0's socket queue-> Guest + VM virtio port 0 Rx burst-> Guest VM 82599 VF port1 Tx burst-> IXIA packet + generator The packet transmission flow is: - IXIA packet generator-> Guest VM 82599 VF port1 rx burst-> Guest VM virtio port 0 tx burst-> tap -> Linux Bridge->82599 PF-> IXIA packet generator + IXIA packet generator-> Guest VM 82599 VF port1 Rx burst-> Guest VM virtio + port 0 Tx burst-> tap -> Linux Bridge->82599 PF-> IXIA packet generator + + +Virtio PMD Rx/Tx Callbacks +-------------------------- + +Virtio driver has 3 Rx callbacks and 2 Tx callbacks. + +Rx callbacks: + +#. ``virtio_recv_pkts``: + Regular version without mergeable Rx buffer support. + +#. ``virtio_recv_mergeable_pkts``: + Regular version with mergeable Rx buffer support. + +#. ``virtio_recv_pkts_vec``: + Vector version without mergeable Rx buffer support, also fixes the available + ring indexes and uses vector instructions to optimize performance. + +Tx callbacks: + +#. ``virtio_xmit_pkts``: + Regular version. + +#. ``virtio_xmit_pkts_simple``: + Vector version fixes the available ring indexes to optimize performance. + + +By default, the non-vector callbacks are used: + +* For Rx: If mergeable Rx buffers is disabled then ``virtio_recv_pkts`` is + used; otherwise ``virtio_recv_mergeable_pkts``. + +* For Tx: ``virtio_xmit_pkts``. + + +Vector callbacks will be used when: + +* ``txq_flags`` is set to ``VIRTIO_SIMPLE_FLAGS`` (0xF01), which implies: + + * Single segment is specified. + + * No offload support is needed. + +* Mergeable Rx buffers is disabled. + +The corresponding callbacks are: + +* For Rx: ``virtio_recv_pkts_vec``. + +* For Tx: ``virtio_xmit_pkts_simple``. + + +Example of using the vector version of the virtio poll mode driver in +``testpmd``:: + + testpmd -c 0x7 -n 4 -- -i --txqflags=0xF01 --rxq=1 --txq=1 --nb-cores=1 |