Re: [Qemu-devel] [Bug 596106] Re: kvm to emulate 64 bit cpu on 32 bit host

[Jamie Lokier <jamie@shareable.org>]

Natalia Portillo wrote:
>    You got the point wrong, I'm talking running WITH 64 bit hardware in a
>    32 bit guest.
>    This is done in Mac OS X Leopard (kernel is only 32 bit) and Mac OS X
>    Snow Leopard (using 32 bit kernel not 64 bit one) by VMWare, Parallels
>    and VirtualBox, as well as on Windows 32 bit using VMWare (dunno about
>    VBox and Parallels, VirtualPC is unable to run 64 bit guests at all
>    even on 64 bit hosts), just provided of course, the hardware is 64
>    bit.

Ah yes, Mac OS X too.

Apart from breaking userspace, the other reason people stick with
32-bit host kernels on both Windows and Macs is the 64-bit device
drivers often don't work properly, or aren't available at all.  They
continue to improve, but still aren't as mature and dependable as
32-bit drivers.

This is also true of Linux 64-bit kernels - both bugs and unavailable
third party drivers/firmware.  (But less so than the other OSes.)
So even with Linux people cannot assume dropping in a 64-bit host
kernel is always free of kernel/driver issues.

Marking this feature request "won't fix" is just a statement that KVM
developers aren't inclined to support this feature.

But there's nothing to stop an interested contributor having a go.
I'm sure if it works and the code is clean enough it will be accepted.

>    VirtualPC is unable to run 64 bit guests at all even on 64 bit
>    hosts

Are you sure?  Microsoft provides numerous downloadable 64-bit guest
Windows images, and VirtualPC is Microsoft's; they must be running on
something.

-- Jamie