I have a working configuration of a Gentoo as a host and a Windows 10 as a guest using QEMU/KVM with GPU passthrough. I also passthrough my keyboard and mouse, and have a secondary keyboard in a different USB port, which is used by the host.

I have installed Synergy on both operating systems, but even thought they share the same IP, I can't get them to see each other with "localhost". I have read that I should rather use bridges, or tun-tap devices, but I can't really understand what they do and would like a bit of help setting them up.

Finally, here is my qemu startup script:

rm /tmp/my_vars.fd
cp /usr/share/edk2.git/ovmf-x64/OVMF_VARS-pure-efi.fd /tmp/my_vars.fd
qemu-system-x86_64 \
-enable-kvm \
-m 6144 \
-smp cores=4,threads=1 \
-soundhw hda \
-usb -device usb-host,hostbus=1,hostaddr=3 \
-usb -device usb-host,hostbus=1,hostaddr=4 \
-device vfio-pci,host=01:00.0,multifunction=on \
-device vfio-pci,host=01:00.1 \
-drive if=pflash,format=raw,readonly,file=/usr/share/edk2.git/ovmf-x64/OVMF_CODE-pure-efi.fd
-device virtio-scsi-pci,id=scsi \
-drive file=/dev/sda5,id=disk,format=raw,if=none -device scsi-hd,drive=disk

1 Answer 1


Your first problem here is that networking is broken on your VM. I wouldn't even think about Synergy until you have that fixed. You say "they share the same IP" That's a problem. In order for them to communicate with eachother they'll need different IP's on the same subnet.

  • And how can I achieve that?
    – FloriOn
    Commented Dec 29, 2015 at 13:26
  • Do you have a DHCP server running or are you assigning IP's manually?
    – David King
    Commented Dec 29, 2015 at 13:29
  • I have no dhcp server running on my PC, but on my router
    – FloriOn
    Commented Dec 29, 2015 at 13:52
  • Then I would configure networking on your host to be in 'bridged' mode. Your VM can get an IP from the router just like any other node on your network and host and guest should be able to communicate.
    – David King
    Commented Dec 29, 2015 at 13:54
  • Would you mind adding some detail or link or something so I can learn more about bridges?
    – FloriOn
    Commented Dec 29, 2015 at 13:55

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