[PATCH] vmx: Parse vm.genid

John Ferlan jferlan at redhat.com
Tue Aug 3 11:48:50 UTC 2021

On 8/2/21 7:00 AM, 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?

Tugging at a memory strand that's 3+ years old results in a blank stare 
followed by some amount of panic ;-)

I do have vague recollections of issues w/ snapshots though - scanning 
the libvirt code for 'genid' or 'GEN_VMID' would seem to give some 
hints. There were some very specific options / processing.

I recall a few qemu patches after the initial implementation, but the 
specifics have long since been erased from the recall buffer. I do see 
Gal who is still at Red Hat did some reviews for the original 
implementation - whether he has any recollections.


> Here's the commit that implemented it in libvirt:
> https://gitlab.com/libvirt/libvirt/-/commit/b50efe97ad1357f9dff26450daf68a7a53201bea
> Michal

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