The virtual machines are observed to undergo a reboot sequence at specific intervals.

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

The issue reported involves virtual machines within a VNF that are facing cyclic reboot issues.

Environment

7.0 U3t

7.0 U3s

Cause

The logs show a series of "hard" and "soft" CPU resets during the reboot process. The "hard" CPU reset is a hardware signal triggering a reset, while the "soft" CPU reset is software-initiated, typically to reinitialize the system’s CPU cores. These resets are common during system-level reboots and don’t necessarily point to any specific error at the ESXi level.

VMware.log

vmware.log:####-##-##T##:##:##.###Z In(05) vcpu-0 - Unknown int 10h func 0x0000
vmware.log:####-##-##T##:##:##.###Z In(05) vcpu-0 - Unknown int 10h func 0x0000
vmware.log:####-##-##T##:##:##.###Z In(05) vcpu-0 - Unknown int 10h func 0x0000

####-##-##T##:##:##.###Z In(05) vcpu-0 - CPU reset: hard (mode Emulation)
####-##-##T##:##:##.###Z In(05) vcpu-2 - CPU reset: hard (mode Emulation)
####-##-##T##:##:##.###Z In(05) vcpu-1 - CPU reset: hard (mode Emulation)


####-##-##T##:##:##.###Z In(05) vcpu-1 - CPU reset: soft (mode Emulation)
####-##-##T##:##:##.###Z In(05) vcpu-2 - CPU reset: soft (mode Emulation)
####-##-##T##:##:##.###Z In(05) vcpu-3 - CPU reset: soft (mode Emulation)

Resolution

It’s recommended to reach out to the vendor of the guest OS to further investigate the issue. The logs indicate "CPU reset: hard (mode Emulation)" and "CPU reset: soft (mode Emulation)", which may suggest an issue related to OS-level or hardware emulation. These types of resets are typically associated with deeper issues within the OS or the underlying hardware emulation, which should be addressed by the OS vendor for a more thorough investigation.

Additional Information

Why do we see a sequence of "CPU reset: hard" followed by "CPU reset: soft" in the vmware.log when a VM performs a soft reboot (e.g. via init 6)?

• A "hard" CPU reset is a hardware signal which causes the CPU to reset itself, such as would occur when the "reset" button on a system's front panel is pressed. A "soft" CPU reset is a software-initiated reset, such as would occur when a CPU asks another to reset itself by sending a Startup Inter-processor Interrupt (SIPI) followed by Init IPIs.
  
  
• A "soft" reboot of the system will still involve a "hard" reset of the CPUs.
  
  
• A "hard" CPU reset will cause the first CPU (the BSP) to start executing firmware (BIOS/EFI) code to reinitialize the system hardware. Very early during firmware initialization, the BSP will initialize and enumerate the other CPU cores, and this requires that "soft" resets be issued to those other CPU cores, resulting in "CPU reset: soft" messages in vmware.log.
  
  
• Once the firmware has passed control to the OS, it is normal for the OS kernel to reinitialize the CPU cores, which involves another round of "soft" resets.