Current status of SqueakNOS is that it runs correctly with old interpreter VMs. We have a plan for making it compatible with new Stack and CogVMs. That would mean performance boosts and also that new pharo and squeak images that are really nicer that ones from some years ago will be compatible. And also that updates on the image would be easily ported to SqueakNOS.
Cheers, Guido.
2012/12/3 Colin Putney colin@wiresong.com
On Mon, Dec 3, 2012 at 10:15 AM, Javier Pimás elpochodelagente@gmail.comwrote:
I never quite understood how Xen compares to things like VMWare or VirtualBox. Is it the same mechanism? What are the differences?
Basically, Xen is a hardware abstraction layer. It takes care of communicating with devices and allocating resources to "domains". What it doesn't provide is virtual hardware. To run on top of Xen you write to an specific ABI, and make "hypercalls" which are analogous to applications making syscalls into an OS kernel. Some operating systems, (e.g., Linux) have been modified to be able to run in this mode, which is called "paravirtualization."
VMware and VirtualBox and KVM on linux provide what is called HVM, with simulated hardware. The guest OS doesn't communicate with Xen via hypercalls, it thinks it's running on actual hardware, dealing with hardware interrupts etc.
Paravirtualization is more efficient than HVM, but it requires special support from the guest OS.
So if SqueakNOS can run on real hardware, it should work fine in HVM. It would probably need some work at the lower levels to support paravirtualization and run directly on Xen.