RE: [PATCH v9 5/8] docs / tools: specific migration v4 to include DOMAIN_CONTEXT

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Sent: 05 October 2020 11:09
> To: Paul Durrant <paul@xxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Paul Durrant <pdurrant@xxxxxxxxxx>; George Dunlap 
> <george.dunlap@xxxxxxxxxx>; Ian Jackson
> <ian.jackson@xxxxxxxxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>; Julien Grall 
> <julien@xxxxxxx>; Stefano
> Stabellini <sstabellini@xxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; Marek 
> Marczykowski-Górecki
> <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> Subject: Re: [PATCH v9 5/8] docs / tools: specific migration v4 to include 
> DOMAIN_CONTEXT
> 
> On 24/09/2020 14:10, Paul Durrant wrote:
> > From: Paul Durrant <pdurrant@xxxxxxxxxx>
> >
> > A new 'domain context' framework was recently introduced to facilitate
> > transfer of state for both PV and HVM guests. Hence this patch mandates the
> > presence of a new DOMAIN_CONTEXT record in version 4 of the libxc migration
> > stream.
> > This record will incorprate the content of the domain's 'shared_info' page
> > and the TSC informaiton so the SHARED_INFO and TSC_INFO records are 
> > deprecated.
> > It is intended that, in future, this record will contain state currently
> > present in the HVM_CONTEXT record. However, for compatibility with earlier
> > migration streams, the version 4 stream format continues to specify an
> > HVM_CONTEXT record and XEN_DOMCTL_sethvmcontext will continue to accept all
> > content of that record that may be present in a version 3 stream.
> >
> > Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> 
> What's the plan for the remainder of the work?  We don't want to burn
> multiple version numbers for each bit of incremental work.
> 
> One option might be to specify the full extent of the work, and use an
> environment variable to alter the behaviour of the sending side, while
> it is still work-in-progress.
> 

The other missing part for transparent migration is xenstore content, but I'd 
expect that to sit at the next level up so I'm not anticipating any more churn 
at this level.

  Paul