Re: [Qemu-devel] OT: Running qemu without host os?

[Jim C. Brown]

On Fri, Jan 21, 2005 at 07:03:18PM +0100, Peter Karlsson wrote:
> On Fri, 21 Jan 2005, Jim C. Brown wrote:
> 
> > >From instead a host OS the virtual (or guest) OS would not know that it is
> > not a real computer. Emulating from the hardware would make this even harder
> > to figure out. The part about giving access to the native hardware directly
> > (instead of access to emulated hardware) is interesting.
> 
> Well, the vm would still have virtualise the hardware wouldn't it? I'm
> thinking of it as like a filter which can let everything, nothing and all
> in between pass through depending on settings. Think of linux virtual
> memory where a process does not know whether it's in real memory or not.

What exactly do you mean by "virtualise the hardware" ?

Qemu already acts as such a filter (except that it has to go thru the host OS
to access the bare metal and that the emulated hardware usually isn't the same
as the hardware the host OS has.)

> 
> > This can still be done in a host OS. The only benefit of using qemu 
> > directly is
> > the factor of speed and RAM usage (you can go faster when you access the 
> > bare
> > metal and you don't have to load up an OS).
> 
> So if I use linux as a host os and run windows 2000 as a vm would qemu let
> windows access for example a radeon 9800xt graphics card via ati's
> official windows drivers?

No, that would be the intriquing part. (Actually, a linux host CAN give that
access, as long as it is a PCI card you are giving the guest access to - but
then only the guest can use it exclusively. Of course Qemu needs to run in X so
this isn't yet possible .. unless you have 2 graphics cards, one of them is
PCI, and the linux host is using the other graphic card.)

> I haven't played with qemu yet and don't know
> it's capabilities but I doubt that the host os would be happy with a
> virtual os taking over the graphics hardware (for instance)...

As long as it is exclusive, it isn't a problem.

> 
> Best regards
> 
> Peter K
> 
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