Looking for detailed info on Config.Defaults.cpuidMask.mode.1.eax

[rsingler]

Looks like it mask the CPUID, but why would you want to do that?  What do the different settings mean?  "mask, clobber"

Google hasn't been much help.

[DSTAVERT · Accepted solution]

CPU masking is used to hide the differences in CPU capabilities in different ESX(i) hosts for vMotion.

http://kb.vmware.com/kb/1993

[AndreTheGiant]

CPU Masking could be a solution.

But if your CPU support EVC, I suggest to use this way... more simple and powerful.

Andre

[bulletprooffool]

Morning,

Have a look at the VMware docs for EVC.

Pretty much, what you are doing is masking portions of the CPU, so that the vCPUs you have presented to your VM have limited instruction sets.

the reason you would want to use this is oif you had a VM clusyter, with differing CPUs in it. If a VM needed to migrate from one to the other and the available instrcution sets were different, the vMotion would fail. If however you reduce the instruction setc on both ESX hosts to the highest common denominator, you can then still vMotion machines between the hosts ad the instructions available are consistent and therefore the vCPUs that they present appear to be the same to the VM.

[rsingler]

Thanks for the answers guys.  My guess is that this setting is left over from their 3.5 days prior to upgrading to 4.x.  I suspected that the setting did what it said it did, but I was having trouble finding it anywhere is documentation.  Thanks again!