I am running Arch Linux with an Intel X520 (82599ES).
I am also running a Windows 10 VM with Qemu/KVM/OVMF.
I have an SR-IOV VF passed through to the VM for networking.
The Windows driver is v. 184.108.40.206 and the Linux driver is the 5.1.0-k ixgbe kernel driver.
I am connecting to a CentOS server through a Mikrotik CSS326 switch. The server also has an X520 NIC and a 10Gb connection to the switch.
Using a Samba share that runs on a FusionIO PCIe SSD on the server, I can comfortably saturate 10Gb on Arch. However, using the same share on the Win 10 VM I can only reach 300MB/s, i.e. exactly 2.5Gbps.
It feels as if my VM is limited to 2.5Gbps instead of being able to use all 10Gb.