я вот хост с виртуалками обновил, но пока не ребутал
Known Issues
VM guests with multiple boot disk setups (e.g., mdadm, LVM, etc...) need to be configured with the new boot order config so that all required disks are marked "bootable", with the one containing the boot loader placed first - otherwise, the guest may fail to boot after being restarted with the new QEMU 5.1 version.