Re: Re: [PATCH] qemu-xen: Fix PV segfault

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Jul 02, 2008 at 03:32:15PM +0100, Ian Jackson wrote:
> John Levon writes ("Re: [Xen-devel] Re: [PATCH] qemu-xen: Fix PV segfault"):
> > On Wed, Jul 02, 2008 at 10:38:32AM +0200, Gerd Hoffmann wrote:
> > > While I'm at it:  There is a patch queue with at
> > > http://kraxel.fedorapeople.org/patches/
> > > 
> > > The plan is to submit that stuff upstream, so regular qemu will have xen
> > > support.  Right now the patch queue has only paravirt bits.  It comes
> > 
> > I'm confused, I thought that was the point of the qemu-xen tree
> 
> Gerd Hoffman's tree seems to be something entirely different.  I'm not
> sure I understand what the point of it is.  The reason why everyone is
> using qemu is that it has all of the hardware emulation device models.
> 
> Qemu proper (ie upstream) also uses the CPU emulator (translator,
> now).  KVM and Xen don't use that because they run the code on the
> physical CPU one way or another.
> 
> Gerd Hoffman's setup doesn't use the device models, nor the CPU
> emulator.  Really as far as I can tell the only thing he wants from
> qemu is the command line parser !  This is quite bizarre as it's not a
> very good command line parser (qemu upstream are considering replacing
> it with something more data-driven and more modular).

It is a derivative of work I did previously to allow qemu-dm to be run
standalone from XenD for starting Xen guests. My proof of concept allowed
you to run both paravirt and fullyvirt guests just be invoking

   qemu-xen -M xenpv -hda /some/path -r 500 

(Change xenpv to xenfv for fullyvirt).  In PV mode it leveraged QEMU for
the graphical framebuffer and text console, to allow VNC and all the
text console options. In FV mode it leveraged all the emulated devices
too. 

Gerd's new code is followig the same idea as my original work but is against
upstream QEMU, instead of ioemu. At this time it only supports PV so is really
only using the CLI parser and text console / VNC server pieces. I believe
he is still planning to add in FV too.

Daniel
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