-.. BSD LICENSE
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- All rights reserved.
-
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- modification, are permitted provided that the following conditions
- are met:
-
- * Redistributions of source code must retain the above copyright
- notice, this list of conditions and the following disclaimer.
- * Redistributions in binary form must reproduce the above copyright
- notice, this list of conditions and the following disclaimer in
- the documentation and/or other materials provided with the
- distribution.
- * Neither the name of Intel Corporation nor the names of its
- contributors may be used to endorse or promote products derived
- from this software without specific prior written permission.
-
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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- OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.. SPDX-License-Identifier: BSD-3-Clause
+ Copyright(c) 2010-2015 Intel Corporation.
Poll Mode Driver for Emulated Virtio NIC
========================================
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 configureable 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.
+ When backend can't support vlan filter, virtio app on guest should not enable vlan filter in order
+ to make sure the virtio port is configured correctly. E.g. do not specify '--enable-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.
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.
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
+ 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
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