Issue 11
© Solarflare Communications 2014
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Solarflare Server Adapter
User Guide
Figure 55: Direct Guest Access to NIC Hardware
It is also worth noting that the networking interface in this model is now a vendor supplied driver
and creation or configuration of networking interfaces must be done via the vendor's driver and not
the standard XenServer network drivers.
Solarflare Plug-in Model
Solarflare, in a collaborated development with Citrix, has implemented a unique unified approach to
SR-IOV that enables accelerated cut-through performance while maintaining full compatibility with
hypervisor-based services and management tools. Solarflare's 254 VFs enable highly scalable
workload consolidation for large data center environments and virtual desktop infrastructure (VDI)
deployments. Unlike other adapters, each Solarflare VF can use multiple DMA channels that enable
the VF to scale over vCPUs using RSS and/or RFS. Solarflare's 2048 DMA channels provide the most
scalable virtualized network I/O solution available in the market.
Solarflare's SR-IOV implementation uses a plug-in approach that maintains the traditional (software)
data path through the XenServer paravirtualized drivers, and then through the vSwitch to the
physical device network driver. In addition, there is an alternative (accelerated) data path through
the VF driver directly to the network adapter from the guest. Packets are received on either data
path transparently to the guest VM's network stack. For transmitted data, the enabled plug-in makes
the decision on whether or not to use the accelerated path. Refer to
With this approach a VM can be created/cloned using traditional tools, and networking to/from the
VM can initially use the standard software network path. Citrix XenServer6 will pass-through a VF
from the network adapter into the guest. The guest identifies that new hardware has been hot
plugged and binds the Solarflare plug-in driver to this VF. This plug-in driver automatically registers
with the Netfront driver as an accelerated network plug-in. Once the VF driver has registered,
subsequent traffic to/from the guest uses the accelerated data path accessing the adapter directly