Tm Host Vm Is Not Suitable For Using Tsc Mode 39-realtscoffset 39- Request To Change Tsc Mode Ignored -

| Aspect | Details | |--------|---------| | | Warning only (not fatal) | | Impact | Slightly less accurate timekeeping in VM | | Fix | Use kvmclock or native TSC mode, or upgrade host CPU/BIOS | | Ignore if | Non-critical VM, no high-resolution timing needs |

GRUB_CMDLINE_LINUX_DEFAULT="tsc=reliable nohz=off"

If your VM does not require high-precision timing (e.g., not running databases, real-time apps, or latency-sensitive workloads), you can safely . The VM will fall back to kvmclock or paravirtualized clocksource , which is often sufficient for general use. | Aspect | Details | |--------|---------| | |

Unlike a static offset ( rdtsc = host_tsc + constant ), the real-time offset is recalculated periodically by the hypervisor to compensate for drift between the host’s TSC and real time. This is essential on systems where the TSC is not invariant (i.e., changes frequency with power states). However, it requires:

When VMware ignores the request to change to Mode 39, it falls back to or Mode 3 (Async Scheduler) . The observable effects include: This is essential on systems where the TSC

This error message typically appears in logs when the hypervisor determines the current hardware or configuration cannot support specific Time Stamp Counter (TSC) modes like RealTscOffset . While this is often just a logged notification, it can be associated with VM hangs or crashes during boot. Potential Causes

tail -100 /vmfs/volumes/datastore/VM_NAME/vmware.log | grep -i "realtscoffset" While this is often just a logged notification,

The VM is configured to request realtscoffset , but the host lacks the necessary stability (e.g., missing invtsc feature).

cpu13:4098760)World: 12345: VM Host is not suitable for using TSC mode 39-realtscoffset- request to change tsc mode ignored cpu13:4098760)World: 12345: Using TSC mode 2 (emulated)

In some edge cases (especially with nested virtualization or Hyper-V/VMware coexistence), the frequency reported by the hypervisor to the guest via cpuid may not match the source used for offset calculation. The mismatch triggers a safety lockout.