Linux Guest OS becomes suspended after reading /dev/port

Products

• VMware vSphere ESXi

Issue/Introduction

• The purpose of this KB is to recommend not to read /dev/port on Linux Guest OS.
• Linux Guest OS may not become suspended if its datastore is not enough to store snapshot.

Symptoms:

• Linux Guest OS becomes suspended after reading /dev/port such as "cat /dev/port".
• In the vmware.log, you see entries similar to:

YYYY-MM-DDTHH:MM:SS.417Z| vcpu-0| I125: PIIX4: PM Suspending to processor level 3 (C3)...

YYYY-MM-DDTHH:MM:SS.463Z| vmx| I125: SUSPEND: Start suspend (flags=0)

YYYY-MM-DDTHH:MM:SS.522Z| vcpu-0| I125: Destroying virtual dev for scsi0:0 vscsi=8197

YYYY-MM-DDTHH:MM:SS.522Z| vcpu-0| I125: VMMon_VSCSIStopVports: No such target on adapter

YYYY-MM-DDTHH:MM:SS.572Z| vcpu-0| I125: Closing all the disks of the VM.

YYYY-MM-DDTHH:MM:SS.572Z| vcpu-0| I125: Closing disk 'scsi0:0'

YYYY-MM-DDTHH:MM:SS.620Z| vcpu-0| I125: DISKLIB-VMFS  : "/vmfs/volumes/<Datastore_uuid>/<VM_Name>/<VM_Name>-flat.vmdk" : closed.

YYYY-MM-DDTHH:MM:SS.865Z| vcpu-0| I125: Progress -1% (msg.checkpoint.saveStatus)

YYYY-MM-DDTHH:MM:SS.866Z| vcpu-0| I125: Checkpointed in VMware ESX, 6.7.0, build-10302608, Linux Host

YYYY-MM-DDTHH:MM:SS.868Z| vcpu-0| I125: Intel VT: FlexPriority disabled in checkpoint.

YYYY-MM-DDTHH:MM:SS.869Z| vcpu-0| I125: Intel VT: FlexPriority disabled in checkpoint.

YYYY-MM-DDTHH:MM:SS.348Z| vcpu-0| I125: Progress 0% (none)

YYYY-MM-DDTHH:MM:SS.348Z| vcpu-0| I125: MainMem: Writing full memory image, '/vmfs/volumes/<Datastore_uuid>/<VM_Name>/<VM_Name>-6bd22366.vmem'.

YYYY-MM-DDTHH:MM:SS.325Z| vcpu-0| I125: Progress 1% (none)

YYYY-MM-DDTHH:MM:SS.278Z| vcpu-0| I125: Progress 2% (none)

YYYY-MM-DDTHH:MM:SS.679Z| vcpu-0| I125: Progress 3% (none)

YYYY-MM-DDTHH:MM:SS.050Z| vcpu-0| I125: Progress 4% (none)

YYYY-MM-DDTHH:MM:SS.299Z| vcpu-0| I125: Progress 5% (none)

YYYY-MM-DDTHH:MM:SS.706Z| vcpu-0| I125: Progress 6% (none)

YYYY-MM-DDTHH:MM:SS.035Z| vcpu-0| I125: Progress 7% (none)

YYYY-MM-DDTHH:MM:SS.491Z| vcpu-0| I125: Progress 8% (none)

 

Environment

VMware vSphere ESXi 7.x
VMware vSphere ESXi 6.7
VMware vSphere ESXi 5.5
VMware vSphere ESXi 6.0
VMware vSphere ESXi 6.5

Cause

• ESXi emulates PIIX4 and reading its PLVL3 I/O port can cause a guest to suspend.
• "cat /dev/port" reads from every possible I/O port including PLVL3 in the I/O address space.

Resolution

• Recommend not to read /dev/port such as "cat /dev/port".

Additional Information

Impact/Risks:

• Linux Guest OS becomes suspended.
• Reading /dev/port can have unknown other side effects and is not safe.