Re: [PATCH v5] docs/designs: re-work the xenstore migration document...

[Edwin Torok <edvin.torok@xxxxxxxxxx>]

On Tue, 2020-05-05 at 14:13 +0100, Jürgen Groß wrote:
> On 05.05.20 15:01, Julien Grall wrote:
> > Hi Paul,
> > 
> > On 28/04/2020 16:06, Paul Durrant wrote:
> > > From: Paul Durrant <pdurrant@xxxxxxxxxx>
> > > 
> > > ... to specify a separate migration stream that will also be
> > > suitable for
> > > live update.
> > > 
> > > The original scope of the document was to support non-
> > > cooperative 
> > > migration
> > > of guests [1] but, since then, live update of xenstored has been 
> > > brought into
> > > scope. Thus it makes more sense to define a separate image format
> > > for
> > > serializing xenstore state that is suitable for both purposes.
> > > 
> > > The document has been limited to specifying a new image format.
> > > The 
> > > mechanism
> > > for acquiring the image for live update or migration is not
> > > covered as 
> > > that
> > > is more appropriately dealt with by a patch to
> > > docs/misc/xenstore.txt. 
> > > It is
> > > also expected that, when the first implementation of live update
> > > or 
> > > migration
> > > making use of this specification is committed, that the document
> > > is 
> > > moved from
> > > docs/designs into docs/specs.
> > > 
> > > NOTE: It will only be necessary to save and restore state for
> > > active 
> > > xenstore
> > >        connections, but the documentation for 'RESUME' in
> > > xenstore.txt 
> > > implies
> > >        otherwise. That command is unused so this patch deletes it
> > > from 
> > > the
> > >        specification.
> 
> Could someone from Citrix please verify that XAPI isn't using
> XS_RESUME?

The implementation of XS_RESUME in oxenstored doesn't do much: it seems
to be just a way for Dom0 to check whether a domain exists or not, and
for a domain to check whether they are Dom0 or not.
If the domain exists, then the resume implementation just returns `()`,
i.e. does nothing.

I can't find any references to Xs.resume in xenopsd (or the other XAPI
repos that I got checked out), so I think it can be safely removed from
the spec and client libraries (I'd keep it in the actual oxenstored
implementation just in case some guest does call it).

Best regards,
--Edwin

> 
> 
> Juergen
>