VME in Microsoft VPC

[AJ]

Hi,

Does anyone know if MS VPC 'officially' does not support Virtual Mode extensions. I have just come across something odd while testing a virtual mode monitor where it GPFs on privileged instructions even with VME enabled. Bochs and Virtualbox (and a real PC!) work fine.

It just struck me as a bit odd because a) VPC runs Windows DOS boxes fine and b) I thought that with the virtualisation used by VPC, the guest processor has the same capabilities as the host and I am using a P4.

I am doing nothing more complex than:

Code: Select all

write_cr4(read_cr4() | CR4_VME);

where write_cr4 and read_cr4 are simple nasm functions.

Cheers,
Adam

[EDIT]Oh, and IOPL is 3![/EDIT]

[bluecode]

Qemu does the same odd thing... It will not complain about enabling VME, but it also GPFs on a priviledged instruction in virtual-8086-mode.