Keyboard lag in VM (libvirt/kvm/qemu/virtio)

Hello,

I have Linux Mint host and i installed EOS (i3) in VM. After some tweaks my machine looks fine except one quite annoying thing. When i type inside VM, there is a little lag which destroys my user expierience

Should i search for solution inside guest or host machine? How to reduce this annoying lag? I was using VMware earlier and similar lag never happened.
Can’t use QXL driver, becouse for some reason screen goes black, so i use virtio with acceleration.

My configuration:

<domain type="kvm">
  <name>endeavour</name>
  <uuid>c03fdfef-8306-4a71-ae6b-8be9b0bdd30b</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://archlinux.org/archlinux/rolling"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory unit="KiB">8388608</memory>
  <currentMemory unit="KiB">8388608</currentMemory>
  <vcpu placement="static">4</vcpu>
  <os>
    <type arch="x86_64" machine="pc-q35-4.2">hvm</type>
    <boot dev="hd"/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <vmport state="off"/>
  </features>
  <cpu mode="host-model" check="partial"/>
  <clock offset="utc">
    <timer name="rtc" tickpolicy="catchup"/>
    <timer name="pit" tickpolicy="delay"/>
    <timer name="hpet" present="no"/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled="no"/>
    <suspend-to-disk enabled="no"/>
  </pm>
  <devices>
    <emulator>/usr/bin/qemu-system-x86_64</emulator>
    <disk type="file" device="disk">
      <driver name="qemu" type="qcow2"/>
      <source file="/media/cysiek/dane/libvirt/test.qcow2"/>
      <target dev="vda" bus="virtio"/>
      <address type="pci" domain="0x0000" bus="0x04" slot="0x00" function="0x0"/>
    </disk>
    <disk type="file" device="cdrom">
      <driver name="qemu" type="raw"/>
      <target dev="sda" bus="sata"/>
      <readonly/>
      <address type="drive" controller="0" bus="0" target="0" unit="0"/>
    </disk>
    <controller type="usb" index="0" model="qemu-xhci" ports="15">
      <address type="pci" domain="0x0000" bus="0x02" slot="0x00" function="0x0"/>
    </controller>
    <controller type="sata" index="0">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x1f" function="0x2"/>
    </controller>
    <controller type="pci" index="0" model="pcie-root"/>
    <controller type="pci" index="1" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="1" port="0x10"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x0" multifunction="on"/>
    </controller>
    <controller type="pci" index="2" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="2" port="0x11"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x1"/>
    </controller>
    <controller type="pci" index="3" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="3" port="0x12"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x2"/>
    </controller>
    <controller type="pci" index="4" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="4" port="0x13"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x3"/>
    </controller>
    <controller type="pci" index="5" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="5" port="0x14"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x4"/>
    </controller>
    <controller type="pci" index="6" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="6" port="0x15"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x5"/>
    </controller>
    <controller type="pci" index="7" model="pcie-root-port">
      <model name="pcie-root-port"/>
      <target chassis="7" port="0x16"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x6"/>
    </controller>
    <controller type="virtio-serial" index="0">
      <address type="pci" domain="0x0000" bus="0x03" slot="0x00" function="0x0"/>
    </controller>
    <filesystem type="mount" accessmode="mapped">
      <source dir="/home/cysiek/exchange"/>
      <target dir="hostshare"/>
      <address type="pci" domain="0x0000" bus="0x07" slot="0x00" function="0x0"/>
    </filesystem>
    <interface type="network">
      <mac address="52:54:00:c8:d1:61"/>
      <source network="default"/>
      <model type="virtio"/>
      <address type="pci" domain="0x0000" bus="0x01" slot="0x00" function="0x0"/>
    </interface>
    <serial type="pty">
      <target type="isa-serial" port="0">
        <model name="isa-serial"/>
      </target>
    </serial>
    <console type="pty">
      <target type="serial" port="0"/>
    </console>
    <channel type="unix">
      <target type="virtio" name="org.qemu.guest_agent.0"/>
      <address type="virtio-serial" controller="0" bus="0" port="1"/>
    </channel>
    <channel type="spicevmc">
      <target type="virtio" name="com.redhat.spice.0"/>
      <address type="virtio-serial" controller="0" bus="0" port="2"/>
    </channel>
    <input type="tablet" bus="usb">
      <address type="usb" bus="0" port="1"/>
    </input>
    <input type="keyboard" bus="usb">
      <address type="usb" bus="0" port="4"/>
    </input>
    <input type="mouse" bus="usb">
      <address type="usb" bus="0" port="5"/>
    </input>
    <input type="mouse" bus="ps2"/>
    <input type="keyboard" bus="ps2"/>
    <graphics type="spice" autoport="yes">
      <listen type="address"/>
      <image compression="off"/>
      <gl enable="no"/>
    </graphics>
    <sound model="ich9">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x1b" function="0x0"/>
    </sound>
    <video>
      <model type="virtio" heads="2" primary="yes">
        <acceleration accel3d="yes"/>
      </model>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x01" function="0x0"/>
    </video>
    <redirdev bus="usb" type="spicevmc">
      <address type="usb" bus="0" port="2"/>
    </redirdev>
    <redirdev bus="usb" type="spicevmc">
      <address type="usb" bus="0" port="3"/>
    </redirdev>
    <memballoon model="virtio">
      <address type="pci" domain="0x0000" bus="0x05" slot="0x00" function="0x0"/>
    </memballoon>
    <rng model="virtio">
      <backend model="random">/dev/urandom</backend>
      <address type="pci" domain="0x0000" bus="0x06" slot="0x00" function="0x0"/>
    </rng>
  </devices>
</domain>

When I was VM-hopping, I ran into the same issue on a couple of guests; same host, but not EOS as the guest. It’s one of the reasons I finally settled on VMware.

From what I can remember, switching the video driver didn’t help. I believe that I had to remove/add a virtual keyboard device, switching between the different virtual types - USB, PS/2 - before it worked again.