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5.7. DPDK in KVM Guests

If you have no access to DPDK supported network cards you can still work with DPDK by using its support for virtio. To do so you have to create guests backed by hugepages (see above).

On top of that there it is required to have at least SSE3. The default CPU model qemu/libvirt uses is only up to SSE2. So you will have to define a model that passed the proper feature flag - and of course have a Host system that supportes it. An example can be found in following snippet to your virsh xml (or the equivalent virsh interface you use).

<cpu mode='host-passthrough'>

This example is rather offensive and passes all host features. That in turn makes the guest not very migratable as the target would need all the features as well. A "softer" way is to just add sse3 to the default model like the following example.

<cpu mode='custom' match='exact'>

<model fallback='allow'>qemu64</model>

<feature policy='require' name='ssse3'/>

</cpu>

Also virtio nowadays supports multiqueue which DPDK in turn can exploit for better speed. To modify a normal virtio definition to have multiple queues add the following to your interface definition. This is about enhancing a normal virtio nic to have multiple queues, to later on be consumed e.g. by DPDK in the guest.

<driver name="vhost" queues="4"/>

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