CPU Feature Management: Lessons from Trenches
summary
Nutanix runs VMs across heterogeneous hosts and documents concrete failures where libvirt and QEMU disagree: pconfig is added in QEMU 3.1 then removed in 4.0 leaving migrations failing between libvirt 4.8 and 5.10; MPX gets dropped from kernel 5.6/QEMU 4.0 but libvirt still advertises it, breaking guest apps and host identification. libvirt reads /var/cache/libvirt/cpu_capabilities via QMP commands like query-cpu-model-expansion; proposal delegates validation to QEMU via an enforce flag and exposes QEMU model versions, with limits to libvirt/QEMU only.
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chapters (7)
- 0:00Start
- 0:31Introduction to Cpu Features
- 6:13Query Cpu Model Expansion
- 9:46Featured Applications
- 16:36Valuation Checks on Host and Guest Cpu Compatibility
- 21:03Problem Statement
- 25:35What Are the Limitations of this Approach
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