How to get best video performance on Windows VM without gpu passtrough?

Question

I'm using OpenSUSE as my main OS on work laptop (Ryzen 5850U, no additional GPU), however I need to have working Outlook desktop app, since some of our company communications are encrypted using S/MIME, which as far as I know is unsupported in OWA on systems other than Windows. We are using on-premise Exchange server.

So I decided to setup Windows VM, I'm using libvirt for this. Here is my VM config:

<domain type="kvm">
  <name>RDPWindows</name>
  <uuid>350141fc-4158-43cc-afad-my-uuid</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://microsoft.com/win/10"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory unit="KiB">8388608</memory>
  <currentMemory unit="KiB">2097152</currentMemory>
  <vcpu placement="static">8</vcpu>
  <os>
    <type arch="x86_64" machine="pc-q35-5.2">hvm</type>
    <loader readonly="yes" type="pflash">/usr/share/qemu/ovmf-x86_64-ms-code.bin</loader>
    <nvram>/var/lib/libvirt/qemu/nvram/RDPWindows_VARS.fd</nvram>
  </os>
  <features>
    <acpi/>
    <apic/>
    <hyperv>
      <relaxed state="on"/>
      <vapic state="on"/>
      <spinlocks state="on" retries="8191"/>
    </hyperv>
    <vmport state="off"/>
  </features>
  <cpu mode="host-model" check="partial">
    <topology sockets="1" dies="1" cores="4" threads="2"/>
  </cpu>
  <clock offset="localtime">
    <timer name="hpet" present="yes"/>
    <timer name="hypervclock" present="yes"/>
  </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="cdrom">
      <driver name="qemu" type="raw"/>
      <source file="/path/to/Windows.iso"/>
      <target dev="sdb" bus="sata"/>
      <readonly/>
      <address type="drive" controller="0" bus="0" target="0" unit="1"/>
    </disk>
    <disk type="file" device="cdrom">
      <driver name="qemu" type="raw"/>
      <source file="/path/to/virtio-win-0.1.208.iso"/>
      <target dev="sdc" bus="sata"/>
      <readonly/>
      <address type="drive" controller="0" bus="0" target="0" unit="2"/>
    </disk>
    <disk type="file" device="disk">
      <driver name="qemu" type="qcow2"/>
      <source file="/var/lib/libvirt/images/win10-office.qcow2"/>
      <target dev="vda" bus="virtio"/>
      <boot order="1"/>
      <address type="pci" domain="0x0000" bus="0x06" slot="0x00" function="0x0"/>
    </disk>
    <controller type="usb" index="0" model="qemu-xhci" ports="15">
      <address type="pci" domain="0x0000" bus="0x03" 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="virtio-serial" index="0">
      <address type="pci" domain="0x0000" bus="0x04" slot="0x00" function="0x0"/>
    </controller>
    <interface type="network">
      <mac address="52:54:00:77:ea:aa"/>
      <source network="default"/>
      <model type="e1000e"/>
      <address type="pci" domain="0x0000" bus="0x01" slot="0x00" function="0x0"/>
    </interface>
    <interface type="network">
      <mac address="52:54:00:e8:2d:aa"/>
      <source network="link-local"/>
      <model type="virtio"/>
      <address type="pci" domain="0x0000" bus="0x02" 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="spicevmc">
      <target type="virtio" name="com.redhat.spice.0"/>
      <address type="virtio-serial" controller="0" bus="0" port="1"/>
    </channel>
    <input type="tablet" bus="usb">
      <address type="usb" bus="0" port="1"/>
    </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="1" primary="yes"/>
      <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>
  </devices>
</domain>

However I'm getting quite poor video performance, it is usable but definitely not convenient to use, so I'm wondering how to get better performance. I tried using https://github.com/Fmstrat/winapps, it gives slightly better performance, but there are visual bugs. I tried RDP with xfreerdp but it wasn't really better than SPICE. I have installed SPICE guest tools on that Windows.

Answer 1

Currently the fastest possible VGA for QEMU/KVM is QXL, at least for usual desktop usage (no 3d support). You've got virtio in your config; probably in the future it'll be the best option, with 3d support. You should change video to something like:

<video>
<model type='qxl' vram='65535' heads='1'>
</model>
</video>

And of course install the drivers. QXL drivers are included in spice-guest-tools (check here spice-guest-tools). You'll also have seamless mouse operation, inside-outside the VM window using a client like spicy or virt-manager's virt-viewer.

Answer 2

Unless you recompile qemu to adjust the GTK UI refresh rate or the upstream decides to make the adjustment you won't ever achieve more than 33fps for mouse movement, which is the annoyance I presume you're facing (you did not provide numbers but only perceptions).

The best options are, assuming your host video graphics and display are satisfactory already:

• qxl/spice but if you're running RHEL on host they are being removed starting in EL9. already missing in OL7.9. ubuntu doesn't appear to have given up.

• remote desktop client to the vm

• a different virtualization solution like VMWare Player

• vnc/teamviewer to the vm with option to disable seeing the remote cursor so you keep the local cursor fps responsiveness. TV can be configured to work only on LAN so no internet exposure, also streams video content pretty decent.