qemu virtio issues after upgrade to 9

[shanreich]

Thank you for your responses. Now I’m a bit wiser. In my opinion, this change came unexpectedly or was not properly tested, or there was not sufficient warning. In my case, the bridge has an MTU of 9000, since the storage is also connected through it. Simply setting the bridge’s MTU to 1500 would lead to a disconnection from the storage. I therefore had to shut down, migrate, and restart each VM – with the result that now all VMs have an MTU of 9000. Do I really have to manually set each VM to an MTU of 1500, damn?! The changes are understandable, but the implementation has caused major issues. Overall, this is very unfortunate.

I understand your frustration with the situation, particularly the migration issue is awkward and @fiona is currently working on improving this situation.

There is a check for this included in pve8to9 though, as well as a note in the release notes [1]. We should probably include this in the upgrade guide as well, I couldn't find it there.

[1] https://wiki.intra.proxmox.com/Release_Notes_PVE#Proxmox_VE_9.0_BETA