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ERROR_HV_PROCESSOR_STARTUP_TIMEOUT
This timeout concerns bringing a physical processor under hypervisor control
ERROR_HV_PROCESSOR_STARTUP_TIMEOUT means a processor did not respond during the hypervisor’s startup sequence. It is lower-level than a guest VP taking too long to boot. Firmware, microcode, processor topology, power-management state, or a host hardware problem can prevent one logical processor from joining the running hypervisor.
Record the host boot event log, firmware and microcode versions, processor topology, and the logical processor that failed. Check whether the issue appears only after resume, firmware changes, or enabling virtualization security. Guest image repair and increasing a VM startup timeout do not address a host processor that never acknowledged hypervisor initialization.
Host evidence to gather
- Logical processor or APIC identity reported during startup.
- BIOS/UEFI, microcode, and chipset firmware versions.
- Recent changes to SMT, virtualization, security, or power settings.
- Whether a cold boot differs from reboot or resume behavior.
References
- Microsoft: processor and firmware requirements for Hyper-V
- Microsoft: Hyper-V host and partition architecture
- Intel: multiprocessor startup and system programming reference
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