Goal

Migration to a host that can't run a VM configuration should be handled gracefully, like on x86_64.

Currently, though the error message is useful, on s390x, the monitor closes unepxectedly:

error: internal error: QEMU unexpectedly closed the monitor (vm='rhel8'): 2024-02-07T10:09:05.877766Z qemu-kvm: Some features requested in the CPU model are not available in the configuration: ctop 

,
whereas on x86_64, libvirt handles this earlier:

# virsh migrate vm2 qemu+ssh://{target_host}/system --live --p2p --copy-storage-all
error: operation failed: guest CPU doesn't match specification: missing features: ds,dtes64,avx512ifma,sha-ni,avx512vbmi,avx512vbmi2,gfni,vaes,vpclmulqdq,avx512bitalg,avx512-vpopcntdq,la57,rdpid,fsrm,wbnoinvd,vmx-page-walk-5

Given that the error message on s390x in itself is useful and the VM keeps running on the source, I open this issue for discussion for improvement of the error handling. Daniel Berrangé reminded me that on s390x CPUs are not handled by libvirt (e.g. no CPU model definitions maintained) though.

Acceptance Criteria

• Given a VM on host 1 with CPU features x1,...,xn that are required by the VM but not available on host 2, when I start a migration, it is canceled with an error message (like on x86_64), e.g.

  error: operation failed: guest CPU doesn't match specification: missing features: x1,...,xn