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@laine.org>
---
src/qemu/qemu_hotplug.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index a1c3ca999b..40c693483e 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -3280,9 +3280,6 @@ qemuDomainAttachWatchdog(virQEMUDriverPtr driver,
if (qemuAssignDeviceWatchdogAlias(watchdog) < 0)
return -1;
- if (!(watchdogstr = qemuBuildWatchdogDevStr(vm->def, watchdog, priv->qemuCaps)))
- return -1;
-
if (watchdog->model == VIR_DOMAIN_WATCHDOG_MODEL_I6300ESB) {
if (qemuDomainEnsurePCIAddress(vm, &dev, driver) < 0)
goto cleanup;
@@ -3294,6 +3291,9 @@ qemuDomainAttachWatchdog(virQEMUDriverPtr driver,
goto cleanup;
}
+ if (!(watchdogstr = qemuBuildWatchdogDevStr(vm->def, watchdog, priv->qemuCaps)))
+ goto cleanup;
+
/* QEMU doesn't have a 'dump' action; we tell qemu to 'pause', then
libvirt listens for the watchdog event, and we perform the dump
ourselves. so convert 'dump' to 'pause' for the qemu cli */
--
2.20.1
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On 1/17/19 4:37 PM, Laine Stump wrote: > 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@laine.org> > --- > src/qemu/qemu_hotplug.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > Reviewed-by: John Ferlan <jferlan@redhat.com> John -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
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