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

[Bayard Bell]

Seems fair enough to require data exchanged between the kernel module  
and user processes in the same bit-ness, but I'm wondering about  
support for larger memory sizes via something like PAE on 32-bit  
systems. The usable memory size is quite sharply limited at 2GB, which  
works well enough for various *nix platforms but not so well for  
Windows. I'm looking to get to a 64-bit system, but moving to Snow  
Leopard is a problem for me, as I'm using ZFS, which is less well  
supported under 10.6, the more so with 64-bit. My preferred option  
would be moving to OpenSolaris, but I need USB support for the  
OpenSolaris host and support for OS X guests. Any chance these  
features have been worked over sufficiently that will be released in  
3.2? PAE would be nice as a transition between the two host  
environments, but I don't sense that there's any intention of  
including this in current release plans. How close to the mark am I  
here?

Von meinem iPhone gesendet

Am 18 Mar 2010 um 22:56 schrieb "Knut St. Osmundsen" <bird at sun.com>:

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