You might be asking, why would anyone want to do this? Well, luckily this is not a "because you can" type of answer but was it was an interesting solution that one of our VMware Engineers (Darius) had shared with me after helping out on this VMTN Community forum thread.
The user was running VMware Fusion on his physical Mac OS X system and wanted to be able to test OS X Mavericks under ESXi. Not having a physical ESXi host to test with, the next best thing was to run a ESXi VM under VMware Fusion and then run the Mavericks guest on top of that.
Here is a quick diagram of the user setup:
The issue with just simply doing this is that for a Mac OS X guest to properly run on ESXi, the underlying hardware must be Apple Hardware. The reason for this is not a technical challenges, but rather a legal one per Apple's EULA. The way in which ESXi detects that the underlying hardware is Apple is by checking whether Apple's SMC (System Management Controller) is available.
In the scenario above, the Nested ESXi VM is not automatically passing through the SMC from the physical Mac OS X system and hence the Mac OS X VM at the very top of the stack will not properly function. The solution that Darius found was to add the following two Advanced VM Settings (VMX) entries to the ESXi VM:
smc.present = "TRUE"
smbios.reflectHost = "TRUE"
This will allow the passing of the underlying SMC up into the Nested ESXi VM which will then allow Mac OS X guest VMs to properly function. We can also confirm this by check the Nested ESXi MOB by pointing a browser to the following URL: https://[ESXI-IP]/mob/?moid=ha-host&doPath=hardware
If you did not add the two entries above, then the smcPresent property would show up as false. In our case, we did add the following two entries and we now run our Mac OS X Guest. Here are a couple of screenshots of performing this on my iMac at home running the same exact configuration:
Thanks Darius for sharing this with me and the community! I am sure this will come in handy for anyone wanting to test Mac OS X guests under ESXi but do not have a physical ESXi host and can easily substitute using VMware Fusion.