Comment 14 for bug 1921754

Before testing with linux 5.11.0-16-generic, qemu 1:5.2+dfsg-9ubuntu2, libvirt 7.0.0-2ubuntu1:

# virsh domcapabilities |grep Milan
# qemu-system-x86_64 -cpu ? | grep Rome
x86 EPYC-Rome (alias configured by machine type)
x86 EPYC-Rome-v1 AMD EPYC-Rome Processor

After installing proposed for qemu/libvirt:

# virsh domcapabilities
    <mode name='host-model' supported='yes'>
      <model fallback='forbid'>EPYC-Milan</model>
      <vendor>AMD</vendor>
      <feature policy='require' name='x2apic'/>
      <feature policy='require' name='tsc-deadline'/>
      <feature policy='require' name='hypervisor'/>
      <feature policy='require' name='tsc_adjust'/>
      <feature policy='require' name='vaes'/>
      <feature policy='require' name='vpclmulqdq'/>
      <feature policy='require' name='spec-ctrl'/>
      <feature policy='require' name='stibp'/>
      <feature policy='require' name='arch-capabilities'/>
      <feature policy='require' name='ssbd'/>
      <feature policy='require' name='cmp_legacy'/>
      <feature policy='require' name='invtsc'/>
      <feature policy='require' name='virt-ssbd'/>
      <feature policy='require' name='rdctl-no'/>
      <feature policy='require' name='skip-l1dfl-vmentry'/>
      <feature policy='require' name='mds-no'/>
      <feature policy='require' name='pschange-mc-no'/>
      <feature policy='disable' name='svme-addr-chk'/>
    </mode>

# qemu-system-x86_64 -cpu ? | grep Rome
x86 EPYC-Rome (alias configured by machine type)
x86 EPYC-Rome-v1 AMD EPYC-Rome Processor
x86 EPYC-Rome-v2 AMD EPYC-Rome Processor

Starting focal instance with:

  <cpu mode='custom' match='exact' check='partial'>
    <model fallback='allow'>EPYC-Rome</model>
    <topology sockets='1' dies='1' cores='1' threads='2'/>
    <feature policy='require' name='amd-ssbd'/>
    <feature policy='require' name='ibrs'/>
  </cpu>

# grep -P 'ssbd|ibrs' /proc/cpuinfo
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm rep_good nopl cpuid extd_apicid tsc_known_freq pni pclmulqdq ssse3 fma cx16 sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm cmp_legacy svm cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw topoext perfctr_core ssbd ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves clzero xsaveerptr wbnoinvd arat npt nrip_save umip rdpid