John,
The feature bit in question is called DCA, which stands for direct cache access. This feature bit was only recently defined and used by CPU vendors, so the older release of ESX that you are using enforces a strict vmotion policy for the feature bit. Newer versions of ESX have determined that this bit is not something that should prevent vmotion, so the new policy is to mask it from the guest and allow it to vary between your source and destination hosts when performing a vmotion.
In general, it is safe to remove these types of masks if you see them, but you should only do so when the VM is powered off. Their main purpose is to prevent unsafe vmotions between differing versions of ESX, and to allow future vmotions to follow the same rules as the VM used previously.
In this particular case, it is best to remove the mask, because it will allow slightly more flexible vmotions without it. If you intend to continue to vmotion this VM between the two ESX versions, however, I would recommend changing the "R" to a "0" (zero), so that you don't get this warning message and to allow the more flexible vmotion behavior no matter where the VM is started. (Note that there may be other vmotion CPUID policy differences between other versions of ESX that this is not the right solution for.)
We are actively looking to improve this mechanism in an upcoming release. Instead, we will track the necessary state internally, and when VMs are power cycled, they will pick up the behavior of the new host automatically.
Please let me know if you have any further questions.
Thanks,
Doug
