How to provide a BIOS Serial to KVM Guests
Step 1: Determine if a lack of BIOS serial number is the problem. On a Windows guest VM, open cmd and run wmic bios get serialnumber. On a Linux guest, run dmidecode -s system-serial-number in terminal.
Anyway, nano /usr/bin/kvm-spice-serial and stick this in it:

under <os> tab i added a line before </os>

<smbios mode=’sysinfo’/>

and after </cputune> i added

 <sysinfo type=’smbios’>
    <bios>
      <entry name=’vendor’>ROG STRIX X570-E GAMING</entry>
      <entry name=’version’>Rev 2802</entry>
      <entry name=’date’>02/24/2020</entry>
    </bios>
    <system>
      <entry name=’manufacturer’>ASUSTeK COMPUTER INC.</entry>
      <entry name=’product’>ROG STRIX X570-E GAMING</entry>
      <entry name=’version’>Rev 2802</entry>
      <entry name=’serial’>191059955402748</entry>
    </system>
    <baseBoard>
      <entry name=’manufacturer’>ASUS</entry>
      <entry name=’product’>ASUSTeK COMPUTER INC.</entry>
      <entry name=’version’>Rev 2802</entry>
      <entry name=’serial’>191059955402747</entry>
    </baseBoard>
  </sysinfo>