If I understand correctly, what you have is
Windows 7 VM hosted by -> ESXi 5.5 VM hosted by -> ESXi (what version???) running on bare metal
For better performance for VMs nested inside the ESXi 5.5 VM, the CPU needs to have VMCS Shadowing. This is an Intel CPU feature is available on Haswell and newer generations (although it does not mean all Haswell and newer CPUs).
Look for the line under the "Host VT-x capabilities" of the vmware.log of the ESXi 5.5 VM. This would indicate the VT-x feature set of the ESXi host running on bare metal.
| vmx| I125: Host VT-x Capabilities:
| vmx| I125: Use VMCS shadowing {0,1}
If it is { 0 }, that means the CPU does not have that feature.
If you scroll further down there should be a "Active HV capabilities" section
| vmx| I125: Active HV capabilities
| vmx| I125: VMCS shadow
You should be able to see a section Guest VT-x Capabilities, and this would be the less capable feature set compared to the Host VT-x capabilities. This is equivalent to indicating what the VT-x capabilities are inside the ESXi 5.5 VM.
I am not sure though if ESXi 5.5 is capable of exploiting VMCS Shadowing as it was released before most of the Haswell server CPUs were released (late 2013, early 2014). Perhaps if you don't see "Use VMCS shadowing" logged that means the ESXi version isn't even aware of the feature.
