Bug 1694170

Summary: [RFE] Support AVIC on AMD CPUs
Product: [oVirt] ovirt-engine Reporter: Ryan <ryan>
Component: GeneralAssignee: bugs <bugs>
Status: CLOSED DEFERRED QA Contact: meital avital <mavital>
Severity: low Docs Contact:
Priority: unspecified    
Version: futureCC: ahadas, bugs, dgilbert, gdeolive, michal.skrivanek, nsimsolo
Target Milestone: ---Keywords: FutureFeature, TestOnly
Target Release: ---Flags: rbarry: needinfo? (nsimsolo)
sbonazzo: ovirt-4.5-
Hardware: x86_64   
OS: Linux   
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Clone Of: Environment:
Last Closed: 2022-04-08 16:34:14 UTC Type: Bug
Regression: --- Mount Type: ---
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oVirt Team: Virt RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:

Description Ryan 2019-03-29 17:06:17 UTC
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

Comment 1 Michal Skrivanek 2020-03-18 15:35:40 UTC
can you please doublecheck the latest state in AV 8.2?

Comment 2 Ryan Barry 2020-03-18 15:48:34 UTC
Nisim, I don't have AMD hardware available. Can you check, please?

Comment 5 Sandro Bonazzola 2022-03-29 16:16:40 UTC
We are past 4.5.0 feature freeze, please re-target.

Comment 6 Michal Skrivanek 2022-04-08 16:34:14 UTC
in 8.6 it may very well work, but closing the bug as we don't seem to have anyone who can verify this