VM migration failure during control-plane-only migration from 4.16 to 4.17 prior to completing control-plane only upgrade to 4.18 or unpausing workers

OCP 4.16.32 -> 4.17.15
CNV 4.16.6 -> 4.17.4

unknown

1. Create VMs
2. Start VM load using stress-ng
3. Pause worker MCP
4. Perform control-plane only upgrade

VM was unable to migrate successfully

All VMs migrated successfully to new virt-launcher pods

Running Cirros VMs with internal stress-ng load
$ stress-ng --iomix 1 --cpu 1 --cpu-load 80 --cpu-load-slice 0 --vm 1 --timeout 0

2000 VMs across 8 nodes

$ oc get vmim -n default -l kubevirt.io/vmi-name=vm-instancetype-cirros-test-1128
NAME                             PHASE       VMI
kubevirt-workload-update-f4n99   Failed      vm-instancetype-cirros-test-1128
kubevirt-workload-update-zqq6d   Succeeded   vm-instancetype-cirros-test-1128

From kubevirt-workload-update-f4n99:
    failureReason: 'Live migration failed error encountered during MigrateToURI3 libvirt api call: virError(Code=1, Domain=0, Message=''An error occurred, but the cause is unknown'')' 


From failed virt-launcher pod:
{"component":"virt-launcher","kind":"","level":"info","msg":"Prepared migration target pod","name":"vm-instancetype-cirros-test-1128","namespace":"default","pos":"server.go:172","timestamp":"2025-02-13T00:40:26.401942Z","uid":"30f75425-0b1c-4ea0-9474-c89aaec297fd"}
{"component":"virt-launcher-monitor","level":"info","msg":"Reaped pid 54 with status 0","pos":"virt-launcher-monitor.go:198","timestamp":"2025-02-13T00:40:27.076025Z"}
{"component":"virt-launcher","level":"error","msg":"Unable to read from monitor: Connection reset by peer","pos":"qemuMonitorIORead:420","subcomponent":"libvirt","thread":"51","timestamp":"2025-02-13T00:41:01.546000Z"}
{"component":"virt-launcher","level":"warning","msg":"Failed to probe capabilities for /usr/libexec/qemu-kvm: Unable to read from monitor: Connection reset by peer","pos":"virQEMUCapsLogProbeFailure:5596","subcomponent":"libvirt","thread":"29","timestamp":"2025-02-13T00:41:01.570000Z"}
{"component":"virt-launcher-monitor","level":"info","msg":"Reaped pid 56 with status 134","pos":"virt-launcher-monitor.go:198","timestamp":"2025-02-13T00:41:01.601941Z"}
{"component":"virt-launcher","kind":"","level":"info","msg":"Signaled target pod virt-launcher-vm-instancetype-cirros-test-1128-6crl8 to cleanup","name":"vm-instancetype-cirros-test-1128","namespace":"default","pos":"server.go:152","timestamp":"2025-02-13T00:41:02.555921Z","uid":"30f75425-0b1c-4ea0-9474-c89aaec297fd"}
panic: received early exit signal
{"component":"virt-launcher-monitor","level":"info","msg":"Reaped pid 10 with status 512","pos":"virt-launcher-monitor.go:198","timestamp":"2025-02-13T00:41:02.661605Z"}
{"component":"virt-launcher-monitor","level":"error","msg":"dirty virt-launcher shutdown: exit-code 2","pos":"virt-launcher-monitor.go:216","timestamp":"2025-02-13T00:41:02.672887Z"}