[PATCH] vmx: Parse vm.genid

[Daniel P. Berrangé]

On Mon, Aug 02, 2021 at 01:00:15PM +0200, Michal Prívozník wrote:
> On 7/30/21 2:02 PM, Richard W.M. Jones wrote:
> > On Thu, Jul 29, 2021 at 10:30:30AM +0200, Michal Privoznik wrote:
> >> The VMware metadata file contains genid but we are not parsing
> >> and thus reporting it in domain XML. However, it's not as
> >> straightforward as one might think. The UUID reported by VMware
> >> is not in its usual string form, but split into two signed long
> >> longs. That means, we have to do a bit of trickery when parsing.
> >> But looking around it's the same magic that libguestfs does:
> >>
> >> https://github.com/libguestfs/virt-v2v/blob/master/v2v/input_vmx.ml#L421
> >>
> >> It's also explained by Rich on qemu-devel:
> >>
> >> https://lists.nongnu.org/archive/html/qemu-devel/2018-07/msg02019.html
> >>
> >> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1598348
> >> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> >> ---
> >>
> >> I've successfully ran vmx2xmltest on an s390x machine which means that
> >> there shouldn't be any endiandness problem.
> >>
> >>  src/vmx/vmx.c                                 | 30 +++++++++++++++++++
> >>  .../vmx2xml-esx-in-the-wild-10.xml            |  1 +
> >>  2 files changed, 31 insertions(+)
> >>
> 
> > 
> > Looked reasonable and seems to match the description here:
> > 
> > https://lists.nongnu.org/archive/html/qemu-devel/2018-07/msg02019.html
> > 
> > Reviewed-by: Richard W.M. Jones <rjones at redhat.com>
> 
> Pushed, thanks.
> 
> > 
> > Out of interest, what is this being consumed by?  I will add this to
> > virt-v2v when it goes upstream.
> 
> I don't recall all the specifics (it was John who implemented it), but
> IIRC it was needed for Windows guests. Something about identifying them
> uniquely. John?

It is supposed to change any time a guest state rolls back. This lets
the guest OS detect when it has been restored from snapshot and take
any actions it considers important. This could be reseting RNG state
to prevent RNG replays, or any number of other things. There is impl
proposed for Linux too

  https://github.com/systemd/systemd/issues/20222

Regards,
Daniel
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