[Xen-devel] Re: [Qemu-devel] [PATCH 05/13] xen: groundwork for xen support

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Gerd Hoffmann writes ("[Qemu-devel] [PATCH 05/13] xen: groundwork for xen 
support"):
> +/*
> + * Figure the environment we are running in.
> + * Returns true when xen is present, false otherwise.
> + * Also checks whenever the domain specified via -domid
> + * exists (so we can attach) or whenever it must be created.
> + */

I don't think this is the right approach.  The intent appears to be
that if you run a particular qemu rune, it will do a completely
different thing when running under Xen.

One bad effect of this is that it is not possible to do a software
emulation of the Xen environment if the host happens to actually be
running under Xen.

The command line, or chosen qemu executable, should specify what qemu
is supposed to do:
  - supporting tasks (hardware emulation etc.)
    for a real Xen domain managed by Xen tools via xenstore etc.
  - software emulation of the Xen environment for the benefit
    of a Xen domU but without using the Xen hypervisor (and
    this should obviously work even if running under Xen0
  - whatever other use cases are important; apparently Gerd
    seems keen to run some code with parts of the xend toolstack
    replaced

Note that of course we have also ported qemu to our embedded minios so
that it can run as a service domain.

> +           "-domid          specify xen guest domain id\n"

Now would be a good time to rename this option to have the word `xen'
in it.

Ian.

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