About offload function of Virtio Nic

[Amos Kong]

Hello all,

Can I ask some question of the offloading function with Virtio-NIC?

I'm interested in KVM virtualization. The virtual NIC is different
from real hardward. And there is also a big distance between
Virtio-NIC and E1000-NIC.
The offloading function of Virtio-NIC close related with the function
of host's real hardware.
Associate Feature bits:
VIRTIO_NET_F_GUEST_...
VIRTIO_NET_F_HOST_...

---------------------------------------------------
command:
enable rx:  guest) # ethtool -K eth0
enable tx:  guest) # ethtool -K eth0
enable gs: guest) # ethtool -K eth0
enable tso: guest) # ethtool -K eth0
enable gso: guest) # ethtool -K eth0
enable lro: guest) # ethtool -K eth0
enable gro: guest) # ethtool -K eth0

Those steps work well with Virtual E1000-NIC, but it always fail when
using Virtio-NIC.

---------------------------------------------------
After setup, I have two check method. For example:
1. enable tso
2. check the output of 'ethtool -k eth0'
3. send large file from guest to host by scp, listen by tcpdump during
transferring file. and check if there contains some large
packet($length > 1514).

The check method works with Virtual E1000-NIC, but it always fail when
using Virtio-NIC.

---------------------------------------------------
My question:
1. How to setup offloading function of Virtio-NIC?
2. How about my check method of offloading function(transferring file,
check packet length by tcpdump)?
3. Is there some detail user guide for Virtio-NIC?



Best Regards,
Amos
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