Re: [PATCH v5] tools/xenstore: add migration stream extensions for new features

[Julien Grall <julien@xxxxxxx>]

Hi Juergen,

On 08/09/2022 09:15, Juergen Gross wrote:
> Extend the definition of the Xenstore migration stream to cover new
> features:
>
> - per domain features
> - extended watches (watch depth)
> - per domain quota
>
> Some of those additions (per domain features and extended watches)
> require bumping the migration stream version to "2", as usage of those
> features will require to transport mandatory new information in the
> migration stream.
>
> One note regarding the GLOBAL_QUOTA_DATA record: the split of quota
> between global and per-domain ones is meant to support the possibility
> to pass on unknown quota settings for newly created domains to other
> Xenstore instances:
>
> Imagine Xenstore A knows about global quota g and domain quota d, while
> Xenstore B doesn't know both. Initially I'm running Xenstore A on a
> host, then I'm live-updating to B.
>
> B gets the information that g is global, and d is per-domain, but has
> no other idea what to do with the values of g and d. OTOH it knows that
> each new domain should get d with the related value, so it can set d
> for each newly created domain.
>
> When B is either downgraded to A again, or a domain is migrated to
> another host running A, B can add the quota information of d for all
> domains.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

--
Julien Grall