Re: [Xen-devel] [PATCH v3 02/17] Document ioemu Linux stubdomain protocol

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Feb 21, 2019 at 06:08:22PM +0100, Marek Marczykowski-Górecki wrote:
> On Thu, Feb 21, 2019 at 03:39:25PM +0000, Wei Liu wrote:
> > On Mon, Jan 28, 2019 at 10:30:19PM +0100, Marek Marczykowski-Górecki wrote:
> > > Add documentation for upcoming Linux stubdomain for qemu-upstream.
> > > 
> > > Signed-off-by: Marek Marczykowski-Górecki 
> > > <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> > > ---
> > >  docs/misc/stubdom.txt | 50 ++++++++++++++++++++++++++++++++++++++++++++-
> > >  1 file changed, 50 insertions(+)
> > > 
> > > diff --git a/docs/misc/stubdom.txt b/docs/misc/stubdom.txt
> > > index 4c524f2..9c94c6b 100644
> > > --- a/docs/misc/stubdom.txt
> > > +++ b/docs/misc/stubdom.txt
> > > @@ -75,6 +75,56 @@ Defined commands:
> > >     - "running" - success
> > >  
> > >  
> > > +Toolstack to Linux ioemu stubdomain protocol
> > > +--------------------------------------------
> > > +
> > > +This section describe communication protocol between toolstack and
> > > +qemu-upstream running in Linux stubdomain. The protocol include
> > > +expectations of both stubdomain, and qemu.
> > > +
> > > +Setup (done by toolstack, expected by stubdomain):
> > > + - Block devices for target domain are connected as PV disks to 
> > > stubdomain,
> > > +   according to configuration order, starting with xvda
> > > + - Network devices for target domain are connected as PV nics to 
> > > stubdomain,
> > > +   according to configuration order, starting with 0
> > > + - [not implemented] if graphics output is expected, VFB and VKB devices 
> > > are set for stubdomain
> > > +   (its backend is responsible for exposing them using appropriate 
> > > protocol
> > > +   like VNC or Spice)
> > > + - other target domain's devices are not connected at this point to 
> > > stubdomain
> > > +   (may be hot-plugged later)
> > > + - QEMU command line is stored in
> > > +   /vm/<target-uuid>/image/dmargs xenstore dir, each argument as 
> > > separate key
> > > +   in form /vm/<target-uuid>/image/dmargs/NNN, where NNN is 0-padded 
> > > argument
> > > +   number
> > > + - target domain id is stored in /local/domain/<stubdom-id>/target 
> > > xenstore path
> > > +?? - bios type is stored in /local/domain/<target-id>/hvmloader/bios
> > 
> > Since you're defining a new protocol here, you have the liberty to
> > eliminate this uncertainty, unless for some reason you want it to be
> > compatible with the old stubdom?
> 
> I'm not sure who access this xenstore key, since I haven't found how is
> it used in minios based stubdomain. Is it used by qemu?

It is read by hvmloader afaict.

Wei.

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