10GB/s network interface on VM (speed is Unknown)

[nockdown]

Proxmox is installed on server with 10GB/s network card.
VM settings: bridge - vmbr0, model - VitriO (paravirtualized).
VM OS: debian 12.6, qemu-guest-agent is installed, qemu-guest-agent status is active (running).
iperf3 shows speed is about 5.2 Gbits/sec on VM:

[ ID] Interval           Transfer     Bandwidth       Retr
[  5]   0.00-10.04  sec  6.07 GBytes  5.20 Gbits/sec  11926             sender
[  5]   0.00-10.04  sec  6.07 GBytes  5.19 Gbits/sec                  receiver

But ethtool on VM shows that speed is Unknown. Ethtool on Proxmox shows that speed is 10000Mb/s.
Is at OK, that ethtool on VM shows that speed is Unknown?
ethtool on VM:

Settings for ens18:
        Supported ports: [  ]
        Supported link modes:   Not reported
        Supported pause frame use: No
        Supports auto-negotiation: No
        Supported FEC modes: Not reported
        Advertised link modes:  Not reported
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Advertised FEC modes: Not reported
        Speed: Unknown!
        Duplex: Unknown! (255)
        Auto-negotiation: off
        Port: Other
        PHYAD: 0
        Transceiver: internal
        Link detected: yes

ethtool on Proxmox:

Settings for enp65s0f3:
        Supported ports: [ FIBRE ]
        Supported link modes:   10000baseT/Full
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: No
        Supported FEC modes: Not reported
        Advertised link modes:  10000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Advertised FEC modes: Not reported
        Speed: 10000Mb/s
        Duplex: Full
        Auto-negotiation: off
        Port: Direct Attach Copper
        PHYAD: 0
        Transceiver: internal
        Supports Wake-on: g
        Wake-on: g
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: yes

 

[_gabriel]

As you pass the NIC over the bridge vmbr0, you are CPU limited.
You can passthrough the entire NIC to the VM to bypass the bridge, but you loose sharing NIC for other VM and host.