[vbox-dev] 64-bit VM build for Mac OS X uses deployment options that break Leopard support

Knut St. Osmundsen bird at sun.com
Thu Mar 18 15:56:21 PDT 2010

On Mar 18, 2010, at 9:50 PM, Bayard Bell wrote:

> As best as I can work out, VirtualBox on Leopard could run 64-bit VM processes to increase the amount of resources available to a VM (this isn't required to allow the VM to run a 64-bit OS, but the 64-bit OS isn't going to have a whole lot of resources available to it if the VM has to run under 32-bit process constraints).

We cannot run the VirtualBox process as 64-bit if the kernel is 32-bit.  The VirtualBox VM process has to use the same number of bits for pointers as the kernel does.  This is mainly because we are sharing data structures between kernel space, but also because lots of code simply assumes that the bit counts match (like R3R0PTRTYPE and all its users). I fear the code will not benefit from trying to address these issues (#ifdef orgy, structure alignment hell, etc.), otherwise we would probably have looked into it by now.

If you want to run a 64-bit VirtualBox on OS X, I suggest you run Snow Leopard with the 64-bit kernel.


Kind regards / Mit freundlichen Gruessen / Vennlig hilsen,


Sun Microsystems GmbH        Knut St. Osmundsen
Werkstrasse 24               Senior Staff Engineer, VirtualBox
71384 Weinstadt, Germany     mailto:bird at sun.com

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