Re: [libvirt] How to best handle the reoccurring of rom changes breaking cross version migrations?

On Thu, Nov 2, 2017 at 4:34 PM, Daniel P. Berrange <berrange(a)redhat.com&gt; wrote: > > On Thu, Nov 02, 2017 at 04:14:06PM +0100, Christian Ehrhardt wrote: >> Ping - since there wasn't any reply so far - any best practices one could >> share? >> >> Let me add a TL;DR: >> - bump of ipxe rom versions change the size of virtio-net-pci.rom >> - that breaks on migration "Length mismatch" >> >> I'd guess the size of that rom has to be fixed up on the fly, but if that >> is really ok and how/where is the question. > > The actual ROM contents will be transferred in the migration stream, so > the fact that the target host has ROMs with different content is not > important. The key thing that matters is that QEMU the target host loads > the ROMs at the same location, so that when the ROM contents is overwritten > with data from the incoming migration scheme, it all ends up at the same > place as it was on the source. Thanks Daniel for your answer, although you try to kill my remaining hopes of a better solution :-) But if the actual ROM content is migrated over anyway "all I'd have to do" is to make clear that the newer system (qemu) knows that the incoming rom has a different size than it thinks. I thought that was what the machine types and their mechanisms were for, but so far I only scratched like 10% of those - maybe they don't cover these rom sizes?