Machine Check Exception (MCE) causing PSOD on ESXi 8.x

Products

• VMware vSphere ESXi

Issue/Introduction

 

• Purple diagnostic screen(PSOD) occurs on an ESXI host with the below back trace and Machine check exception message ( this specific case indicates a hardware failure detected by the CPU)


  Machine Check Exception on PCPU## in world ######:nsx-appctl
System has encountered a Hardware Error - Please contact the hardware vendor

  SRAR Excp G7 BI Sb988880808180134 AO M86 PO/0 Cache Hierarchy: Level 0 Data Cache DataRead Error

  cr0=0x80010031 cr2=0x39a0c95000 cr3=0x4085897800 cr4=0x142768
FMS=06/55/7 uCode=0x5803901
frame=0x452940505eb0 ip=0x428034c17872 err=0x12 rflags=0x10216

  

 

• Alternative MCE message:
  
  Uncorrectable Machine Check Exception (Processor 1, APIC ID 0x00000000, Bank 0x00000006, Status 0xBA000000'00000E0B, Address 0x00000000'00000000, Misc 0x00000000'4D380000).
  
  
  
  

Environment

• VMware vSphere ESXi 8.x
• Physical Server Hardware (HPE, Dell, Lenovo, Cisco)

Cause

The Machine Check Architecture (MCA) is a CPU feature designed to detect and report hardware anomalies. When the hardware detects a critical or fatal condition, it raises a Machine Check Exception (MCE). These exceptions are considered severe and unrecoverable, which leads to an expected ESXi host crash, often resulting in a Purple Screen of Death (PSOD).
In this scenario, the MCE was categorized as an SRAR (System Reset Assert Register), which denotes:

• Uncorrectable: The error cannot be automatically corrected by hardware.
• Recoverable: A system-level action could theoretically mitigate the issue.
• Action Required: Specific corrective steps, such as terminating the thread accessing the affected Memory Page Number (MPN), are needed

The faulty thread was executing within the vmkernel context the ESXi host was unable to isolate or terminate it. This results in the MCE being escalated to a fatal system error, leading to a crash.

Resolution

 

Resolution

1. Reboot the Host: Restart the physical server to restore temporary functionality.
2. Verify Hardware Health: Review the Integrated Management Log (IML) or System Event Log (SEL) for specific hardware faults (CPU, Memory, or PCIe).
3. Engage Hardware Vendor: Provide the captured MCE data to the server vendor for hardware diagnostics.
4. Firmware Compliance: Ensure the server BIOS and component firmware match the versions listed in the VMware Compatibility Guide.