Technical Details: eSwitch Legacy Mode

Legacy mode is the default state of the Intel® Ethernet Controller E810's eSwitch. It is how the eSwitch does hardware switching in a traditional network controller with SR-IOV.

In SR-IOV, there is a PCIe PF per external LAN port, and there is an eSwitch per {PF: LAN port} pair that connects all the VF Virtual Station Interfaces (VSIs) attached to the external port. Each VF has its own PCI configuration space, so software resources associated for data transfer are directly available to the VF and are isolated from use by the other VFs and the PF. When SR-IOV VFs are assigned to a VM in pass-through mode, the system IOMMU controls and protects memory access. This is the reason why host admin or PF has limited control over VF hardware configuration once the VF is assigned to VM/VNF or container.

The VF is a light-weight PCI function that can do only a limited number of tasks compared to the PF—mostly transmit and receive. However, it can do this directly to the VF hardware, thus achieving the goal of bypassing the hypervisor for I/O operations.

In this mode, configuration and filters configured through OVS-TC or the Linux Bridge for VFs are used only in software switching (vSwitch) without hardware switching support. MAC and VLAN hardware-level filters for the VF are configured automatically by PF driver and only these filters (VLAN/MAC) are configured in the hardware eSwitch for hardware switching.