Even though the number of configured vCPUs in the VM wasn't changed nor excessive, a VM wouldn't cross-migrate (got an EVC error) hot.

After powering off the VM and migrating to another cluster, which was on the same EVC level, powering on the VM resulted in the error "Module 'CPUID' power on failed."

Inspecting the CPU Identification Mask settings (Edit Settings -> CPU > CPUID Mask -> Advanced) and resetting to default did not resolve the issue.

I assumed the VMX had some clues, and found multiple lines of cpuid-related flags:

[aners@derp:/vmfs/volumes/vsan:5..2]grep -i cpu *.vmx:

...
sched.cpu.units = "mhz"
cpuid.80000001.edx = "---- ---- ---0 ---- ---- ---- ---- ----"
cpuid.80000001.eax.amd = "---- ---- ---- ---- ---- ---- ---- ----"
cpuid.80000001.ebx.amd = "---- ---- ---- ---- ---- ---- ---- ----"
cpuid.80000001.ecx.amd = "---- ---- ---- ---- ---- ---- ---- ----"
cpuid.80000001.edx.amd = "---- ---- ---0 ---- ---- ---- ---- ----"
sched.cpu.latencySensitivity = "normal"
...

Removing all 'cpuid...'-lines from the VMX resolved the issue, the VM was now able to boot.