Comment 31 for bug 1915063

Ok, so you should be able to drop these lines one by one:

      <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='stibp'/>
      <feature policy='require' name='arch-capabilities'/>
      <feature policy='require' name='ssbd'/>
      <feature policy='require' name='xsaves'/>
      <feature policy='require' name='cmp_legacy'/>
      <feature policy='require' name='invtsc'/>
      <feature policy='require' name='amd-ssbd'/>
      <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'/>

If that does not yet make it work, add those one by one (removing the features of the named type)
    <feature policy='disable' name='3dnowprefetch'/>
    <feature policy='disable' name='abm'/>
    <feature policy='disable' name='adx'/>
    <feature policy='disable' name='aes'/>
    <feature policy='disable' name='amd-stibp'/>
    <feature policy='disable' name='apic'/>
    <feature policy='disable' name='arat'/>
    <feature policy='disable' name='avx'/>
    <feature policy='disable' name='avx2'/>
    <feature policy='disable' name='bmi1'/>
    <feature policy='disable' name='bmi2'/>
    <feature policy='disable' name='clflush'/>
    <feature policy='disable' name='clflushopt'/>
    <feature policy='disable' name='clwb'/>
    <feature policy='disable' name='clzero'/>
    <feature policy='disable' name='cmov'/>
    <feature policy='disable' name='cr8legacy'/>
    <feature policy='disable' name='cx16'/>
    <feature policy='disable' name='cx8'/>
    <feature policy='disable' name='de'/>
    <feature policy='disable' name='f16c'/>
    <feature policy='disable' name='fma'/>
    <feature policy='disable' name='fpu'/>
    <feature policy='disable' name='fsgsbase'/>
    <feature policy='disable' name='fxsr'/>
    <feature policy='disable' name='fxsr_opt'/>
    <feature policy='disable' name='ibpb'/>
    <feature policy='disable' name='lahf_lm'/>
    <feature policy='disable' name='lm'/>
    <feature policy='disable' name='mca'/>
    <feature policy='disable' name='mce'/>
    <feature policy='disable' name='misalignsse'/>
    <feature policy='disable' name='mmx'/>
    <feature policy='disable' name='mmxext'/>
    <feature policy='disable' name='movbe'/>
    <feature policy='disable' name='msr'/>
    <feature policy='disable' name='mtrr'/>
    <feature policy='disable' name='npt'/>
    <feature policy='disable' name='nrip-save'/>
    <feature policy='disable' name='nx'/>
    <feature policy='disable' name='osvw'/>
    <feature policy='disable' name='pae'/>
    <feature policy='disable' name='pat'/>
    <feature policy='disable' name='pclmuldq'/>
    <feature policy='disable' name='pdpe1gb'/>
    <feature policy='disable' name='perfctr_core'/>
    <feature policy='disable' name='pge'/>
    <feature policy='disable' name='pni'/>
    <feature policy='disable' name='popcnt'/>
    <feature policy='disable' name='pse'/>
    <feature policy='disable' name='pse36'/>
    <feature policy='disable' name='rdpid'/>
    <feature policy='disable' name='rdrand'/>
    <feature policy='disable' name='rdseed'/>
    <feature policy='disable' name='rdtscp'/>
    <feature policy='disable' name='sep'/>
    <feature policy='disable' name='sha-ni'/>
    <feature policy='disable' name='smap'/>
    <feature policy='disable' name='smep'/>
    <feature policy='disable' name='sse'/>
    <feature policy='disable' name='sse2'/>
    <feature policy='disable' name='sse4.1'/>
    <feature policy='disable' name='sse4.2'/>
    <feature policy='disable' name='sse4a'/>
    <feature policy='disable' name='ssse3'/>
    <feature policy='disable' name='svm'/>
    <feature policy='disable' name='syscall'/>
    <feature policy='disable' name='tsc'/>
    <feature policy='disable' name='umip'/>
    <feature policy='disable' name='vme'/>
    <feature policy='disable' name='wbnoinvd'/>
    <feature policy='disable' name='xgetbv1'/>
    <feature policy='disable' name='xsave'/>
    <feature policy='disable' name='xsavec'/>
    <feature policy='disable' name='xsaveerptr'/>
    <feature policy='disable' name='xsaveopt'/>

Eventually I'd hope you identify one feature (re add everything but this to verify) that breaks it. Any chance to do this iterative test? You could also "bisect" this list if you want to save some time.