Vmware was Re: Announcing shell machine availability for dragonfly developers

Matthew Dillon dillon at apollo.backplane.com
Fri Aug 29 10:03:30 PDT 2003

    I have used bochs too.  It's been improved considerably from earlier
    versions but, of course being an instruction-by-instruction emulator,
    it is slower then VMWare.  On the otherhand Bochs is entirely usermode
    and has no chance of crashing your system, something I have managed
    to do with vmware on occassion :-).

    It occurs to me that we could implement a full address space abstraction
    for DragonFly which would allow normal user programs to use the entire
    address space.  Once that were done it would only be a small step to
    implement a usermode 'emulation' layer which allows one user program to
    intercept privileged instructions and address accesses that another tries
    to run.  Then we could implement something similar to VMWare ourselves
    and probably achieve 70-80% native operation.  It would be an interesting
    project, anyway.

					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>

:> > Vmware is an excellent product, although expensive.  I haven't tried
:> > Bochs but I imagine that would also work (although at a far lower speed)
:> > and it's OSS.
:> I can vouch for bochs, it works quite well on a 1Ghz Celeron.  You can even
:> compile it with a remote gdb stub - essential for this kind of work.
:Also take a look at QEMU, which uses dynamic translation to
:virtualise the system.  QEMU achieves around 25% of native
:speed, despite being fully emulated...
:It also makes it way easier to debug a kernel then using eg.
:vmware, because you can more easily look inside the qemu
:virtual machine.  The disadvantage is that QEMU doesn't yet
:do full MMU emulation, which means you need to build a
:special kernel to use with QEMU (different address space
:layout, but that's basically it).

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