qemu: fix hot unplug of PCI devices with VFIO

Currently, on hot unplug of PCI devices with VFIO driver for QEMU, libvirt is
trying to restore the host devices to it's previous value (basically a chown
on the previous user/group).

However for devices with VFIO driver, when the device is unbinded it is
removed from the /dev/vfio file system causing the restore label to fail.

The fix is to not restore the label for those PCI devices since they are going
to be teared down anyway.
Signed-off-by: NLudovic Beliveau <ludovic.beliveau@windriver.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_hotplug.c

@@ -1278,7 +1278,8 @@ qemuDomainAttachHostPCIDevice(virQEMUDriverPtr driver,
     if (virSecurityManagerSetHostdevLabel(driver->securityManager,
                                           vm->def, hostdev, NULL) < 0)
         goto error;
-    teardownlabel = true;
+    if (backend != VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO)
+        teardownlabel = true;
 
     if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE)) {
         if (qemuAssignDeviceHostdevAlias(vm->def, hostdev, -1) < 0)
@@ -2985,6 +2986,8 @@ qemuDomainRemoveHostDevice(virQEMUDriverPtr driver,
     int ret = -1;
     qemuDomainObjPrivatePtr priv = vm->privateData;
     char *drivestr = NULL;
+    int backend;
+    bool is_vfio = false;
 
     VIR_DEBUG("Removing host device %s from domain %p %s",
               hostdev->info->alias, vm, vm->def->name);
@@ -3028,6 +3031,8 @@ qemuDomainRemoveHostDevice(virQEMUDriverPtr driver,
 
     switch ((virDomainHostdevSubsysType) hostdev->source.subsys.type) {
     case VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_PCI:
+        backend = hostdev->source.subsys.u.pci.backend;
+        is_vfio = backend == VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO;
         qemuDomainRemovePCIHostDevice(driver, vm, hostdev);
         /* QEMU might no longer need to lock as much memory, eg. we just
          * detached the last VFIO device, so adjust the limit here */
@@ -3047,7 +3052,8 @@ qemuDomainRemoveHostDevice(virQEMUDriverPtr driver,
     if (qemuTeardownHostdevCgroup(vm, hostdev) < 0)
         VIR_WARN("Failed to remove host device cgroup ACL");
 
-    if (virSecurityManagerRestoreHostdevLabel(driver->securityManager,
+    if (!is_vfio &&
+        virSecurityManagerRestoreHostdevLabel(driver->securityManager,
                                               vm->def, hostdev, NULL) < 0) {
         VIR_WARN("Failed to restore host device labelling");
     }