Re: [Xen-devel] [PATCH 5/6] libxl: allow a generation ID to be specified at domain creation

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-06-10 at 14:41 +0100, David Vrabel wrote:
> On 10/06/14 14:37, Ian Campbell wrote:
> > On Tue, 2014-06-10 at 13:35 +0100, David Vrabel wrote:
> >> On 10/06/14 12:01, Ian Campbell wrote:
> >>> On Tue, 2014-06-03 at 14:15 +0100, David Vrabel wrote:
> >>>> Toolstacks may specify a VM generation ID using the
> >>>> u.hvm.generation_id field into libxl_domain_build_info structure, when
> >>>> creating a domain.
> >>>>
> >>>> The toolstack is responsible for providing the correct generation ID
> >>>> according to the Microsoft specification (e.g., generating new random
> >>>> ones as appropriate when restoring).
> >>>
> >>> Any reason not to make the libxl interface a (def)bool and have libxl
> >>> generate a suitable ID internally? Does anything ever care about the
> >>> specific UUID?
> >>
> >> Other toolstacks (like xapi) have a better idea of the life-cycle of a
> >> VM than xl does and thus need only use a new ID for snapshots -- they
> >> can retain the same ID if the domain is just rebooted/migrated.
> > 
> > They should set the field to false then and libxl won't regenerate it.
> 
> They still need an interface to specify the ID.

Oh, because of the reboot case. That makes sense.

> I don't see any value in adding a use_random_genid field just to avoid a
> single libxl_uuid_generate() call in the toolstack.

The point is to get as much common stuff into the library as we can, but
as you've now made clear this isn't common.

Ian.


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