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

From: Wei Liu <wei.liu2@citrix.com>
To: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Wei Liu <wei.liu2@citrix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
	Julien Grall <julien.grall@arm.com>,
	Jan Beulich <jbeulich@suse.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v3 02/17] Document ioemu Linux stubdomain protocol
Date: Thu, 21 Feb 2019 17:31:54 +0000	[thread overview]
Message-ID: <20190221173154.onisjck5hgk7s67k@zion.uk.xensource.com> (raw)
In-Reply-To: <20190221170822.GU21228@mail-itl>

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@invisiblethingslab.com>
> > > ---
> > >  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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