Virtio is a para-virtualization framework initiated by IBM, and supported by KVM hypervisor.
In the Data Plane Development Kit (DPDK),
we provide a virtio Poll Mode Driver (PMD) as a software solution, comparing to SRIOV hardware solution,
+
for fast guest VM to guest VM communication and guest VM to host communication.
Vhost is a kernel acceleration module for virtio qemu backend.
which enables vhost to directly read/ write packets from/to a physical port.
With this enhancement, virtio could achieve quite promising performance.
-In future release, we will also make enhancement to vhost backend,
-releasing peak performance of virtio PMD driver.
-
For basic qemu-KVM installation and other Intel EM poll mode driver in guest VM,
please refer to Chapter "Driver for VM Emulated Devices".
* 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 2.7 and below.
If given a different descriptor number by the upper application,
the virtio PMD generates a warning and fall back to the hard-coded value.
+ Rx queue size can be configurable and up to 1024 since qemu 2.8 and above. Rx queue size is 256
+ by default. Tx queue size is still hard-coded to be 256.
* Features of mac/vlan filter are supported, negotiation with vhost/backend are needed to support them.
When backend can't support vlan filter, virtio app on guest should disable vlan filter to make sure
the virtio port is configured correctly. E.g. specify '--disable-hw-vlan' in testpmd command line.
-* RTE_PKTMBUF_HEADROOM should be defined larger than sizeof(struct virtio_net_hdr), which is 10 bytes.
+* "RTE_PKTMBUF_HEADROOM" should be defined
+ no less than "sizeof(struct virtio_net_hdr_mrg_rxbuf)", which is 12 bytes when mergeable or
+ "VIRTIO_F_VERSION_1" is set.
+ no less than "sizeof(struct virtio_net_hdr)", which is 10 bytes, when using non-mergeable.
* Virtio does not support runtime configuration.
* Virtio supports Link State interrupt.
+* Virtio supports Rx interrupt (so far, only support 1:1 mapping for queue/interrupt).
+
* Virtio supports software vlan stripping and inserting.
* Virtio supports using port IO to get PCI resource when uio/igb_uio module is not available.
.. code-block:: console
- examples/kni/build/app/kni -c 0xf -n 4 -- -p 0x1 -P --config="(0,1,3)"
+ examples/kni/build/app/kni -l 0-3 -n 4 -- -p 0x1 -P --config="(0,1,3)"
This command generates one network device vEth0 for physical port.
If specify more physical ports, the generated network device will be vEth1, vEth2, and so on.
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
modprobe uio
echo 512 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages
modprobe uio_pci_generic
- python tools/dpdk_nic_bind.py -b uio_pci_generic 00:03.0
+ python usertools/dpdk-devbind.py -b uio_pci_generic 00:03.0
We use testpmd as the forwarding application in this 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
--------------------------------
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 -l 0-2 -n 4 -- -i --txqflags=0xF01 --rxq=1 --txq=1 --nb-cores=1
+
+
+Interrupt mode
+--------------
+
+.. _virtio_interrupt_mode:
+
+There are three kinds of interrupts from a virtio device over PCI bus: config
+interrupt, Rx interrupts, and Tx interrupts. Config interrupt is used for
+notification of device configuration changes, especially link status (lsc).
+Interrupt mode is translated into Rx interrupts in the context of DPDK.
+
+.. Note::
+
+ Virtio PMD already has support for receiving lsc from qemu when the link
+ status changes, especially when vhost user disconnects. However, it fails
+ to do that if the VM is created by qemu 2.6.2 or below, since the
+ capability to detect vhost user disconnection is introduced in qemu 2.7.0.
+
+Prerequisites for Rx interrupts
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To support Rx interrupts,
+#. Check if guest kernel supports VFIO-NOIOMMU:
+
+ Linux started to support VFIO-NOIOMMU since 4.8.0. Make sure the guest
+ kernel is compiled with:
+
+ .. code-block:: console
+
+ CONFIG_VFIO_NOIOMMU=y
+
+#. Properly set msix vectors when starting VM:
+
+ Enable multi-queue when starting VM, and specify msix vectors in qemu
+ cmdline. (N+1) is the minimum, and (2N+2) is mostly recommended.
+
+ .. code-block:: console
+
+ $(QEMU) ... -device virtio-net-pci,mq=on,vectors=2N+2 ...
+
+#. In VM, insert vfio module in NOIOMMU mode:
+
+ .. code-block:: console
+
+ modprobe vfio enable_unsafe_noiommu_mode=1
+ modprobe vfio-pci
+
+#. In VM, bind the virtio device with vfio-pci:
+
+ .. code-block:: console
+
+ python usertools/dpdk-devbind.py -b vfio-pci 00:03.0
+
+Example
+~~~~~~~
+
+Here we use l3fwd-power as an example to show how to get started.
+
+ Example:
+
+ .. code-block:: console
+
+ $ l3fwd-power -l 0-1 -- -p 1 -P --config="(0,0,1)" \
+ --no-numa --parse-ptype
Code Review / deb_dpdk.git / blobdiff