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Retrieving and translating CPUID features for a vSphere VM

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Whether you are using the classic Enhanced vMotion Compatibility (EVC) on a vSphere Cluster or the new Per-VM EVC capability, the usable (user-level) CPU features from an ESXi host are then presented down into a Virtual Machine for consumption.

If you wanted to see what which CPU features are exposed for a particular VM or even custom CPU compatibility mask which hides certain CPU features, you can do so by using the vSphere API and accessing either the FeatureRequirement or FeatureMask properties, depending if Per-VM EVC is configured or not. The results from the vSphere API is a list of CPUID strings that may or may not be easy to translate to the friendly CPU processor feature name.

While doing some testing, I noticed that for VMs configured with Per-VM EVC, rather than listing out the CPUID strings, it actually lists the friendly CPU processor feature name.


I was not able to find any CPUID translator using the EvcManager API, but the vSphere UI must be getting this information somehow, right? After a bit of poking around in my vCenter Server Appliance (VCSA), I realized how this translation was occurring ...

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Enabling/Disabling EVC using the vSphere MOB

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There were some discussions this morning on twitter regarding the configuration of EVC for a vSphere Cluster using one of the vSphere CLI's such as PowerCLI or directly leveraging the vSphere API. Unfortunately, this is not possible today as the operations pertaining to EVC are not currently exposed in the vSphere API. This means you will not be able to use the vCLI, PowerCLI, vCO or the vSphere API to configure and manage EVC configurations, you will need to use the vSphere Client to do so.

Having said that, one could still "potentially" automate EVC configurations using the vSphere MOB interface using the private vSphere API, but it may not be ideal and will require some "creativity" and custom coding to integrate with your existing automation solution. This particular limitation of the vSphere API is one that I have personally faced and have filed a bug with VMware awhile back. I am hoping this will eventually be added to the public vSphere API, so that users can fully automate all aspects and configurations of a vSphere Cluster.

Disclaimer: This is not officially supported by VMware, use at your own risk and discretion.

Step 1 - Connect to your vCenter MOB and traverse to the vSphere Cluster of interest (note the MOID will be different in your specific cluster).

Step 2 -  Now replace the URL with the following while substituting the cluster MOID that you see in your browser:

https://reflex.primp-industries.com/mob/?moid=domain-c1550&method=transitionalEVCManager

and hit enter and you'll be brought to TransitionalEVCManager() method, you'll then want to click on the "Invoke Method". Once you do so, you should be returned with a task object and you'll have a link to something like evcdomain-cXXXX. Click on this and you'll be brought to ClusterTransitionalEVCManager.

Step 3 - From here you'll have have some basic evcState information which you can click on to see what the current EVC configuration is set to, guaranteedCPUFeatures and valid EVC Modes (the last part will be important for reconfiguring EVC)

Step 4 - Now let's say the cluster currently has EVC Mode set to intel-merom and you would like to change it to Nehalem, you would need to retrieve the key from the previous page, in our example it's intel-nehalem. Now, you need to click on the method link called ConfigureEVC_Task which is pretty straight forward, it just accepts the EVC Mode Key, enter the string and click on "Invoke Method" and now your cluster will be reconfigured if you go back to the evcState or look at your vCenter task. You can also disable EVC by using DisableEVC_Task

 
Note: If EVC is already configured in your vSphere Cluster, you can use the vSphere API to view it's current configuration by looking at the ClusterComputeResource's summary property. You just will not be able to make any changes or disabling EVC using the vSphere API.

How to Configure Nested ESXi 5 to Support EVC Clusters

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Dave Hill recently wrote an article about running nested ESXi and a gotcha with EVC (Enhanced vMotion Compatibility). In vSphere 4.x, you could not join a nested ESXi host into a cluster with EVC enabled. With vSphere 5, there's actually a way to connect a nested ESXi 5 host to an EVC enabled cluster AND still power on 64bit nested guestOSes.

I have to thank my friend and partner in crime Tuan Duong for showing me this trick awhile back. Tuan was performing some tests using both nested and physical ESXi 5 hosts and discovered this method after a bit of tinkering. At the time, I was not sure if others would find this useful and I did not document the process.

Disclaimer: As usual, this is not officially supported by VMware, use at your own risk. 

Here are the steps:

1. You must be running vSphere 5, create a nested ESXi 5 host using this article How to Enable Support for Nested 64bit & Hyper-V VMs in vSphere 5

2. Create an EVC enabled cluster or use an existing cluster with whatever baseline you would like and click on the "Current CPUID Details" in cluster settings.

3. Copy down the CPU mask flags for that particular EVC baseline, you will need this in the next step

4. Shutdown your nested ESXi 5 host and edit the VM's settings and under "Options" tab click on "CPUID Mask->Advanced". You will take the CPU mask from the above step and update the nested ESXi 5 VM to make it match

5. Go ahead and power on your nested ESXi 5 host and join it to the EVC enabled cluster you created earlier. You should not see any errors when connecting to the cluster and after that you can create a nested 64bit VM within that virtualized ESXi 5 host.

There you have it, running a nested ESXi 5 host and joined to an EVC enabled cluster! Isn't VMware technology awesome! 🙂