Re: [libvirt] [PATCH] qemu: fix i6300esb watchdog hotplug on Q35

When commit 361c8dc17 added support for hotplugging the i6300esb watchdog device (first in libvirt-3.9.0), it accidentally contstructed the commandline for the device_add command before allocating a PCI address for the device. With no PCI address specified in the command, the watchdog would simply be placed at the lowest unused PCI slot. On a 440fx guest, this doesn't cause a problem, because libvirt's PCI address allocation algorithm would most likely give the same address anyway (usually a slot on pci-root), so nobody noticed the omission of address from the command. But on a Q35 guest, the lowest unused PCI slot is on pcie-root, which doesn't support hotplug; libvirt knows enough to assign a PCI address that is on a pcie-to-pci-bridge (because its slots *do* support hotplug), but qemu doesn't, so if there is no PCI address in the command, qemu just tries to plug the new device into pcie-root, and fails because it doesn't support hotplug, e.g.: error: Failed to attach device from watchdog.xml error: internal error: unable to execute QEMU command 'device_add': Bus 'pcie.0' does not support hotplugging The solution is simply to build the command string after assigning a PCI address, not before. Resolves: https://bugzilla.redhat.com/1666559 Signed-off-by: Laine Stump <laine(a)laine.org&gt; --- src/qemu/qemu_hotplug.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)