Help whith network device model

We are using VirtIO (paravirtualized) on all Vm's as network device model, because admin guide say that is " aim for maximum performance".

But we are detecting that on the os vms installed (ubuntu) the nic is --> configuration: autonegotiation=off, Auto-negotiation: off (command used lshw or ethtool) , but if we use Intel E1000 the nic is --> configuration: autonegotiation=on.

Why happens this, is correct ?

~# ethtool eth0
Settings for eth0:
Supported ports: [ ]
Supported link...

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