Bug 1694170

Description of problem:

Cannot use AVIC with AMD CPUs. AVIC helps accelerate interrupts in virtual environments. If AVIC is enabled oVirt reports the CPU type as unsupported because AVIC conflicts with x2apic. The x2apic flag is added to every CPU model by default when kvm is enabled (see the RHEL bug below).

Enabling AVIC worked under 4.2, but 4.3 seems to be more strict with detecting CPU features/capabilities.

See the following bugzilla reports for more information:
Initial oVirt report for unsupported CPU type:
https://bugzilla.redhat.com/show_bug.cgi?id=1674265

RHEL Bug for x2apic flag requirement, and details the problem at the qemu/libvirt level:
https://bugzilla.redhat.com/show_bug.cgi?id=1675030

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Set host to maintenance mode.
2. Set the kvm module option 'options kvm_amd avic=1'.
3. Clear the capabilities cache rm -f /var/cache/libvirt/qemu/capabilities/*.xml
4. Reboot the host or reload the kvm module and restart libvirtd
5. Try to activate the host.

Actual results:
Reports CPU type as unsupported.

Expected results:
Host activates, can use AVIC. Either oVirt ignores the x2apic flag mismatch or directly supports the AVIC flag.

Additional info:
Tested on AMD EPYC 7551P