Configure CPU Model

To configure a CPU model:

The correct CPU model should be configured for a KVM guest to mitigate Fatal glibc error: CPU does not support x86-64-v2. To view the bug, refer to Bug 2040657 - glibc: More Reliable CPU Compatibility Diagnostics.

To determine the current architecture level (on KVM guest or compute resource), the following cpu_check.awk script can be used:

#!/usr/bin/awk -f

BEGIN {
    while (!/flags/) if (getline < "/proc/cpuinfo" != 1) exit 1
    if (/lm/&&/cmov/&&/cx8/&&/fpu/&&/fxsr/&&/mmx/&&/syscall/&&/sse2/) level = 1
    if (level == 1 && /cx16/&&/lahf/&&/popcnt/&&/sse4_1/&&/sse4_2/&&/ssse3/) level = 2
    if (level == 2 && /avx/&&/avx2/&&/bmi1/&&/bmi2/&&/f16c/&&/fma/&&/abm/&&/movbe/&&/xsave/) level = 3
    if (level == 3 && /avx512f/&&/avx512bw/&&/avx512cd/&&/avx512dq/&&/avx512vl/) level = 4
    if (level > 0) { print "CPU supports x86-64-v" level; exit level + 1 }
    exit 1
}

To determine architecture levels inside the guest, run:
```
# ./cpu_check.awk
CPU supports x86-64-v1
```
To check the architecture level on compute resource:
```
# ./cpu_check.awk
CPU supports x86-64-v3
```

ABI compatibility levels for CPU models, preferred CPU models for Intel x86, and AMD x86 compute resources are described at QEMU / KVM CPU model configuration.

To determine the CPU model on compute resource, run:

# virsh capabilities
<capabilities>

  <host>
    ...
    <cpu>
      <arch>x86_64</arch>
      <model>EPYC-IBPB</model>
      <vendor>AMD</vendor>

To set the needed model for the KVM guest, the following should be added to its libvirt XML configuration file (Configuring the CPU model):
```
<domain type="kvm" xmlns:qemu="http://libvirt.org/schemas/domain/qemu/1.0">
...
<cpu mode="custom">
  <model>EPYC-IBPB</model>
</cpu>
```