Cross-Generation VM Live Migration
VM live migration allows a VM to be migrated from one physical host to another without interrupting the VM running. The key benefit of cross-generation migration lies in its ability to maintain VM operation and service continuity during hardware upgrades by supporting migration between different hardware generations. Successful implementation typically requires sufficient compatibility between source and target hardware platforms, and hardware discrepancy tolerance at the VM OS and application layers. While technically challenging, this capability significantly enhances operational flexibility for data centers and cloud service providers by ensuring continuous service availability.
Specifications
Supported VM specifications include but are not limited to 2 vCPUs with 8 GB memory, 4 vCPUs with 8 GB memory, 4 vCPUs with 16 GB memory, 8 vCPUs with 16 GB memory, 16 vCPUs with 32 GB memory, and 32 vCPUs with 64 GB memory.
Version Requirements
- Version: Only kernel 6.6 and QEMU 8.2.0 are supported.
- License: none.
Application Scenarios
Cross-generation VM live migration applies to online service migration in hardware maintenance, disaster recovery (DR) for high availability (HA), and hardware upgrade. It performs memory dirty page replication and device status transfer on running VMs so that the VMs can be migrated from older-generation servers to next-generation servers without stopping the VMs. Enterprises can migrate services on old physical machines in batches during off-peak hours at night, achieving seamless hardware phase-out, rack replacement, and computing power upgrade in a short cutover window.
General Constraints
- VMs running on the Kunpeng 920 processor can only be unidirectionally migrated to the new Kunpeng 920 processor model.
- Cross-generation live migration requires disabling features that are not included in the minimum feature set, as they may cause performance deterioration. The minimum feature set includes features supported by both generations of processors.
- Cross-generation live migration applies only to VMs configured with features in the minimum feature set. As such, running VMs (usually configured with complete chip features) need to be restarted with features only in the minimum feature set enabled, while unstarted VMs can be directly started with features only in the minimum feature set enabled.
- All functions of cross-generation live migration are developed based on kernel 6.6 and QEMU 8.2.0. You need to upgrade the host kernel and QEMU to the corresponding versions and apply the cross-generation live migration function patch.
- Customers need to upgrade the guest kernel to include the Errata live migration framework.
- The Syscount frequency must be consistent between processors. The value for the Kunpeng 920 processor is 100 MHz, while that for the new Kunpeng 920 processor model is 100 MHz or 1 GHz. Therefore, you need to set the frequency to 100 MHz in the BIOS menu.
- Only GICv3 and GICv4.1 support live migration, and live migration can be performed only when the same GIC version is used. When GICv3 is used, the BIOS GIC version is not restricted but the source and destination must use the same version, and GICv4.0-related content must be disabled in the OS boot option. When GICv4.1 is used, GICv4.1 must be enabled in the BIOS and the OS boot option.
- Whether VF passthrough devices support cross-generation live migration depends on the devices themselves.
- The functional compatibility of features in the minimum feature set between different generations depends on the actual verification.
- PMU migration is not supported.
- Do not directly migrate the programs compiled on a later processor model to earlier ones.