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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@laine.org>
Reviewed-by: John Ferlan <jferlan@redhat.com>
This commit is contained in:
Laine Stump 2019-01-17 15:05:54 -05:00
parent 01ca4010d8
commit 40136bd316
1 changed files with 3 additions and 3 deletions
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6
src/qemu/qemu_hotplug.c
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@ -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 */