Re: [PATCH] vmx: Parse vm.genid

On Mon, Aug 02, 2021 at 12:26:56PM +0100, Richard W.M. Jones wrote: > On Mon, Aug 02, 2021 at 12:12:08PM +0100, Daniel P. Berrangé wrote: > > On Mon, Aug 02, 2021 at 12:04:49PM +0100, Richard W.M. Jones wrote: > > > 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(a)redhat.com&gt; > > > > >> --- > > > > >> > > > > >> 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(a)redhat.com&gt; > > > > > > > > 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? > > > > > > Sure, I understand what it's used for. I was just wondering if there > > > are other consumers who want to pull the genID from VMware VMX files > > > using libvirt. Seems like something quite specific to V2V scenarios. > > > > Could there even be a a case to be made for V2V to *not* preserve the > > the genID value. eg If you see a genID in the existing config, then > > write a /different/ genID value in the new VM, to indicate that this > > new VM is a fork of the original VM ? > > https://images5.alphacoders.com/405/405572.jpg > > Noooo! Successfully converted VMs are definitely not forks and > shouldn't be used that way. Are we sure it doesn't end up that way indirectly. eg is there any liklihood that people will do this sequence: 1. Stop original guest 2. Run virt-v2v 3. Start converted guest 4. Find something not right 5. Stop converted guest 6. Start original guest 7. Fix <something> 8. Goto (1) Step 5/6 here is effectively akin to rolling back to a saved snapshot. Thus genID ought to change if this is something users are liable todo.