VirtualBox + VirtualPC2007 = crash

[HackAR]

Host:
Win7 SP1 x64
Core2 Quad CPU

VirtualBox:
WinXP x32 SP3
Hardware acceleration enabled

VirtualPC 2007:
Win98 SE
Hardware acceleration enabled

VirtualBox started first with WinXP. Once VirtualPC is booting Win98, VirtualPC crashes (log included). If I try to start the crashed WinXP, the host crashes with BSOD (see included minidump)
The issue seems to be the hardware acceleration: if I deactivate the support in VirtualPC2007, no crash occurs.

[Mihai Hanor]

This is not a bug. Read the VirtualBox manual about running VirtualBox at the same time with other hypervisors and hardware virtualization enabled.

[HackAR]

Ok, I agree, that starting VirtualPC2007 can crash a guest on VirtualBox, if VirtualPC does something bad :)
However, I do not believe, that a BSOD while restarting a guest on VirtualBox cannot be prevented. (Since VirtualPC manages to start perfectly while VirtualBox is using hardware acceleration)

[jlittle]

I'm hitting what sounds like the same issue as this, and can provide my own minidump if necessary. Host is Windows 7 64 bit, VirtualBox guest is Windows 7 64 bit, VirtualPC guest is Windows 7 32 bit.

I believe the documentation mhanor is referring to is at ​http://www.virtualbox.org/manual/ch10.html in the "Hardware vs. software virtualization" section. I understand that running multiple hypervisors is not supported and that this could be classified as "not a bug" for that reason. But is there really nothing that can be done to prevent a BSOD here? I hit this problem 3 times yesterday, *not* when trying to run Virtual PC at the same time as VirtualBox, but when trying to start VirtualBox *after* previously running and then shutting down a VirtualPC VM. Presumably VirtualPC is holding on to the VT resources somehow and causing this problem, but it is disconcerting to predictably get a BSOD when starting VirtualBox at some later time.

Unfortunately it doesn't seem to be possible to disable VirtualPC's use of hardware virtualization in Windows 7, and disabling hardware virtualization entirely is not an option since it's required for 64 bit guests.

I was able to reproduce the original report here and as pointed out by HackAR, VirtualPC does not cause a BSOD when started with VirtualBox running and using the VT hardware. To my naive point of view that means it should be possible to do something about this that's better than bringing the whole OS down...