Re: [PATCH v4 2/2] virtio_net: Extend virtio to use VF datapath when available

Thu, Mar 01, 2018 at 09:08:43PM CET, sridhar.samudrala@intel.com wrote:

This patch enables virtio_net to switch over to a VF datapath when a VF
netdev is present with the same MAC address. It allows live migration
of a VM with a direct attached VF without the need to setup a bond/team
between a VF and virtio net device in the guest.

The hypervisor needs to enable only one datapath at any time so that
packets don't get looped back to the VM over the other datapath. When a VF
is plugged, the virtio datapath link state can be marked as down. The
hypervisor needs to unplug the VF device from the guest on the source host
and reset the MAC filter of the VF to initiate failover of datapath to
virtio before starting the migration. After the migration is completed,
the destination hypervisor sets the MAC filter on the VF and plugs it back
to the guest to switch over to VF datapath.

When BACKUP feature is enabled, an additional netdev(bypass netdev) is
created that acts as a master device and tracks the state of the 2 lower
netdevs. The original virtio_net netdev is marked as 'backup' netdev and a
passthru device with the same MAC is registered as 'active' netdev.

This patch is based on the discussion initiated by Jesse on this thread.
https://marc.info/?l=linux-virtualization&m=151189725224231&w=2

Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
Signed-off-by: Alexander Duyck <redacted>
Reviewed-by: Jesse Brandeburg <redacted>
---
drivers/net/virtio_net.c | 683 ++++++++++++++++++++++++++++++++++++++++++++++-

As I wrote to the discussion of the other version of this patchset,
I strongly believe you need to have a common part in net/core/ that will
be shared by both virtio_net and netvsc. There there should be explicit
limits for this in-driver bonding solution, like max 1 vf slave, etc.