ESXi hosts might fail with a purple diagnostic screen when a VM issues SCSI -2 command with bus sharing set to Physical.

Products

• VMware vSphere ESXi

Issue/Introduction

• ESXi host fails with a purple diagnostic screen (PSOD).

• The issue occurs when a virtual machine configured with Physical bus sharing issues a SCSI-2 command.

• From /var/core/vmkernel-zdump, we can see back trace similar to:

  • YYYY-MM-DDTHH:MM:SS.MS cpu95:165224071)Backtrace for current CPU #95, worldID=165224071, fp=0xXXXXXXXXXXXXXXXX
    YYYY-MM-DDTHH:MM:SS.MS cpu95:165224071)0xXXXXXXXXXXXXXXXX:[0xXXXXXXXXXXXXXXXX]MCSLockWork@vmkernel#nover+0x8
    YYYY-MM-DDTHH:MM:SS.MS cpu95:165224071)0xXXXXXXXXXXXXXXXX:[0xXXXXXXXXXXXXXXXX]VSCSI_CmdPermittedOnPersResv@vmkernel#nover+0x121
    YYYY-MM-DDTHH:MM:SS.MS cpu95:165224071)0xXXXXXXXXXXXXXXXX:[0xXXXXXXXXXXXXXXXX]VSCSI_FSCommand@vmkernel#nover+0x1119
    YYYY-MM-DDTHH:MM:SS.MS cpu95:165224071)0xXXXXXXXXXXXXXXXX:[0xXXXXXXXXXXXXXXXX]VSCSI_IssueCommandBE@vmkernel#nover+0x35
    YYYY-MM-DDTHH:MM:SS.MS cpu95:165224071)0xXXXXXXXXXXXXXXXX:[0xXXXXXXXXXXXXXXXX]VSCSIExecuteCommandInt@vmkernel#nover+0x4e7
    YYYY-MM-DDTHH:MM:SS.MS cpu95:165224071)0xXXXXXXXXXXXXXXXX:[0xXXXXXXXXXXXXXXXX]PVSCSI_ProcessRing@vmkernel#nover+0x118
    YYYY-MM-DDTHH:MM:SS.MS cpu95:165224071).[45m.[33;1mVMware ESXi 7.0.3 [Releasebuild-20036589 x86_64].[0m

Environment

• VMware vSphere ESXi 7.x

Cause

• When the SCSI controller’s bus sharing is set to Physical, a legacy SCSI-2 command may still be issued by the guest OS.

• SCSI-2 reservations are not supported on ESXi.

• When such an unsupported command is issued, the ESXi storage stack mishandles the request, causing a purple diagnostic screen (PSOD).

Resolution

• This issue has been fixed in VMware vSphere ESXi 7.0 U3i
• For more information, refer to: ESXi 7.0 U3i Release Notes