Symptoms
Linux Guest OS becomes suspended after reading /dev/port such as "cat /dev/port".In the vmware.log, you see entries similar to:
2018-12-17T04:29:51.417Z| vcpu-0| I125: PIIX4: PM Suspending to processor level 3 (C3)...
2018-12-17T04:29:51.463Z| vmx| I125: SUSPEND: Start suspend (flags=0)
2018-12-17T04:29:51.522Z| vcpu-0| I125: Destroying virtual dev for scsi0:0 vscsi=8197
2018-12-17T04:29:51.522Z| vcpu-0| I125: VMMon_VSCSIStopVports: No such target on adapter
2018-12-17T04:29:51.572Z| vcpu-0| I125: Closing all the disks of the VM.
2018-12-17T04:29:51.572Z| vcpu-0| I125: Closing disk 'scsi0:0'
2018-12-17T04:29:51.620Z| vcpu-0| I125: DISKLIB-VMFS : "/vmfs/volumes/5bf90342-9056c317-29b1-005056b051a0/Web-Tier-ubuntu/Web-Tier-ubuntu-flat.vmdk" : closed.
2018-12-17T04:29:51.865Z| vcpu-0| I125: Progress -1% (msg.checkpoint.saveStatus)
2018-12-17T04:29:51.866Z| vcpu-0| I125: Checkpointed in VMware ESX, 6.7.0, build-10302608, Linux Host
2018-12-17T04:29:51.868Z| vcpu-0| I125: Intel VT: FlexPriority disabled in checkpoint.
2018-12-17T04:29:51.869Z| vcpu-0| I125: Intel VT: FlexPriority disabled in checkpoint.
2018-12-17T04:29:52.348Z| vcpu-0| I125: Progress 0% (none)
2018-12-17T04:29:52.348Z| vcpu-0| I125: MainMem: Writing full memory image, '/vmfs/volumes/5bf90342-9056c317-29b1-005056b051a0/Web-Tier-ubuntu/Web-Tier-ubuntu-6bd22366.vmem'.
2018-12-17T04:30:04.325Z| vcpu-0| I125: Progress 1% (none)
2018-12-17T04:30:09.278Z| vcpu-0| I125: Progress 2% (none)
2018-12-17T04:30:09.679Z| vcpu-0| I125: Progress 3% (none)
2018-12-17T04:30:10.050Z| vcpu-0| I125: Progress 4% (none)
2018-12-17T04:30:10.299Z| vcpu-0| I125: Progress 5% (none)
2018-12-17T04:30:10.706Z| vcpu-0| I125: Progress 6% (none)
2018-12-17T04:30:11.035Z| vcpu-0| I125: Progress 7% (none)
2018-12-17T04:30:11.491Z| vcpu-0| I125: Progress 8% (none)
Purpose
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.
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.
Impact / Risks
Linux Guest OS becomes suspended.Reading /dev/port can have unknown other side effects and is not safe.
Resolution
Recommend not to read /dev/port such as "cat /dev/port".
