For the full history behind this patch, look at the following: https://issues.redhat.com/browse/RHEL-7036 commit v10.7.0-101-ga37bd2a15b commit v10.8.0-rc2-8-gbcd5ae4e73 Summary: original problem was unexpected failure of update-device when the user hadn't changed anything other than online status of the guest NIC (which should always be allowed). The first commit "fixed" this by avoiding the allocation of a new ActualNetDef (i.e. creating a new networkport) for *all* network device updates (because that was inappropriately changing which ethernet physdev should be used for a macvtap connection, which by design can't be handled in an update-device). But this commit caused a regression for update-device of bridge-based network devices (because some the updates of certain attributes *do* require the ActualNetDef be re-allocated), so... The 2nd commit narrowed the list of network types that get the "don't allocate new ActualNetDef" treatment (so that only interfaces connected to a network that uses a pool of ethernet VFs *being used in passthrough mode* qualify). But then it was pointed out that this re-broke simple updates of devices that used a direct/macvtap network in "bridge" mode (because it's possible to list multiple physdevs to use for bridge mode, in which case the network driver attempts to "load balance" (and so a new allocation might have a different ethernet physdev which, again, can't be supported in a device-update). So this (single line of code) patch *widens* the list of network types that don't allocate a new ActualNetDef to also include the other direct (macvtap) modes, e.g. bridge, private, etc. Signed-off-by: Laine Stump <laine(a)redhat.com&gt; --- There is a more comprehensive fix that also, e.g., makes updating the bandwidth or vlan info of a direct interface work correctly, but that is much more invasive (and also isn't done yet). This patch fixes the case of updating a direct interface's online status (for example) without breaking anything else. src/qemu/qemu_hotplug.c | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-) diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c index 3c18af6b0c..ff8c1263c6 100644 --- a/src/qemu/qemu_hotplug.c +++ b/src/qemu/qemu_hotplug.c @@ -3935,25 +3935,29 @@ qemuDomainChangeNet(virQEMUDriver *driver, if (newdev->type == VIR_DOMAIN_NET_TYPE_NETWORK) { if (olddev->type == VIR_DOMAIN_NET_TYPE_NETWORK && oldType == VIR_DOMAIN_NET_TYPE_DIRECT && - virDomainNetGetActualDirectMode(olddev) == VIR_NETDEV_MACVLAN_MODE_PASSTHRU && STREQ(olddev->data.network.name, newdev->data.network.name)) { /* old and new are type='network', and the network name - * hasn't changed *and* this is a network where each - * connection is allocated exclusive use of a VF - * device. In this case we *don't* want to get a new port - * ("actual device") from the network because attempting - * to allocate a new device would also allocate a - * new/different VF, causing the update to fail. And - * anyway we can use olddev's actualNetDef (since it - * hasn't changed). - * - * So instead we just duplicate *the pointer to* the - * actualNetDef from olddev to newdev so that comparisons - * of actualNetDef will show no change. If the update is - * successful, we will clear the actualNetDef pointer from - * olddev before destroying it (or if the update fails, - * then we need to clear the pointer from newdev before - * destroying it) + * hasn't changed *and* this is a "direct" network (a pool + * of 1 or more host ethernet devices where each guest + * interface is allocated one device that it connects to + * via macvtap. In this case we *don't* want to get a new + * port ("actual device") from the network because + * attempting to allocate a new device would also allocate + * a new/different ethernet, causing the update to fail + * (because the physical device of a macvtap-based + * interface can't be changed without completely + * unplugging and re-plugging the guest NIC). + + + * We can work around this issue by just re-using olddev's + * actualNetDef (since it hasn't changed) rather than + * allocating a new one. We just duplicate *the pointer + * to* the actualNetDef from olddev to newdev so that + * comparisons of actualNetDef will show no change. If the + * update is successful, we will clear the actualNetDef + * pointer from olddev before destroying it (or if the + * update fails, then we need to clear the pointer from + * newdev before destroying it) */ newdev->data.network.actual = olddev->data.network.actual; memcpy(newdev->data.network.portid, olddev->data.network.portid, -- 2.47.0