Nested virtualization - no VT-x/AMD-V

[ender2101]

Hi, guys

Recently I've noticed, that virtualization extensions aren't properly discovered under nested virualization: say we have host OS running VirtualBox Master, which runs guest OS with another VirtualBox installed (Slave). Although enabled in Master, these options are not available for system, which Slave is installed in (instruction sets reported are MMX, SSE (1, 2, 3, 3S), EM64T).
Anybody experienced such a problem before?

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&r

[Sasquatch]

This is by design. It doesn't make sense to use VT-x/AMD-V and provide the same CPU feature, which is locked now anyway, to the Guest OS. Same idea as running a VB Guest with VT-x enabled, and try to run another virtualisation program with the same settings. Just won't do. Besides, VT-x/AMD-V is made for direct access to the CPU from the Host. The Guest never has direct CPU access. The hypervisor has.

[ender2101]

It doesn't make sense to use VT-x/AMD-V and provide the same CPU feature, which is locked now anyway.

Well, apart from whether it makes sens or it doesn't - for me, all the "virtualization" is about, is a possibility of getting the environment virtually undistinguishable from the original one. Of course, I know - normally you'd rather not do that as each step of such a virtualization reduces efficiency. Nevertheless having such an opportunity sounds just exciting for me.
Many thanks for your response anyway.