Arch qemu
Red Hat Enterprise Linux Server release 7.5 (Maipo) Several days ago, I reproduced this bug in RHEL-7.5 occasionally in the following comment.īut tried for many times, I can not reproduce it any more in neither RHEL-7.5 or RHEL7.6, will continue to do more research.
ARCH QEMU UPDATE
Probably a good idea, to make sure customers update their configurations before trying to live migrate. On the QEMU side: make "+arch-facilities" a migration blocker. This would keep existing VMs working, but may confuse a running guest. On the QEMU side: make "+arch-facilities" a no-op. This could break libvirt feature checks in the same way as removing the feature unconditionally. On the QEMU side: keep "arch-facilities" working, but always report it as unavailable.
This would prevent existing VMs using the "arch-facilities" feature from running. On the QEMU side: removing the "arch-facilities" feature unconditionally. On the libvirt side: make mode="host-model" never enable arch-facilities.Īdditional actions that are (or were) being considered:
ARCH QEMU PATCH
Problem was detected by code analysis while reviewing the patch for bug 1633150. But fixing it as soon as possible in a 7.6.z update will make sure less customers will have new VMs created with the broken arch-facilities CPU feature. It will be difficult to fix this without breaking existing VM configurations. "arch-facilities" should never be enabled in a VM. "arch-facilities" is in the domain XML after the VM is started. Version-Release number of selected component (if applicable):Ĭreate VM with mode="host-model" on a host having arch_capabilities on /proc/cpuinfo Now qemu-kvm reports arch-facilities as a supported feature, mode="host-model" will enable arch-facilities in the domain XML, and we have a VM that can't be safely live-migrated. Then the 7.6 kernel was updated, and ARCH_CAPABILITIES was added to GET_SUPPORTED_CPUID. QEMU called the feature "arch-capabilities", but live-migration support for the feature isn't available yet (neither upstream or in the RHEL qemu-kvm package). The upstream kernel added support to ARCH_CAPABILITIES later. This was not a problem in RHEL-7.5 because KVM never reported the feature on GET_SUPPORTED_CPUID.
"arch-facilities" was a feature that was never included in the 7.5 kernel, but was added to the CPU feature table in qemu-kvm. When using mode="host-model" on a 7.6 host, libvirt may inadvertently enable the "arch-facilities" feature in the domain XML.