Please see description in BZ 2128929. The following combination is illegal as the address 0x2.0x5 is invalid on a pcie root port: -device '{"driver":"pcie-root-port","port":21,"chassis":6,"id":"pci.6","bus":"pcie.0","addr":"0x2.0x5"}' \ {"execute":"device_add","arguments":{"driver":"virtio-net-pci","netdev":"hostnet1","mac":"00:11:22:33:44:03","id": "net1","bus":"pci.6","addr":"0x2.0x5"}} Add a warning to let users know they are using an invalid configuration. This has already been fixed upstream with this commit: https://gitlab.com/qemu-project/qemu/-/commit/ca92eb5defcf9d1c2106341744a73a03cf26e824 We can test this bug when we rebase QEMU to version 8.1 or above and mark it as fixed upon rebase.