Cannot read TPR

[confusedsushi]

I recently upgraded to VirtualBox 4.1.2, unfortunately I having some trouble with it.

Reading of the TPR does not seem to function, I tracked the problem down to the fact that reading the TPR just not return anything.

Reading is done by:

mov eax, DWORD PTR [ecx+edx]

with ecx holding the mapped APIC base address and edx the offset to the TPR. After the Instruction which seemed to be replaced by a vmmcall the eax register is not modified at all.

I remembered that my old virtual system which was set up with a Version of VirtualBox 3 running in VirtualBox 4.0.10 I don't had the problem, so I downgraded to 4.0.10, but still the problem, but the interesting thing is, that when i start the old virtual system I don't experience the problem.

[confusedsushi]

I should add that my guest is running Windows XP.

Further investigation showed that this problem also exist with 4.0.12, but only with the Guest Additions of version 4.0.12 or higher. If I leave the Guest Additions in the version of 4.0.10 everything is fine.

I also noticed that with the older Guest Additions the access to the TPR is not replaced by a vmmcall instruction.

[Klaus Espenlaub]

If you observe any different APIC behavior with and without guest additions this would be a bug: the guest additions do not change anything in this area.

Are you 100% sure that you're comparing setups which are running in the same virtualization mode?

Please provide VBox.log for a VM where it does work, and for a VM where it doesn't.

[Frank Mehnert]

No response, closing.