This reverts commit 2841e675.
It turns out that adding the host_mtu field to the PCI capabilities in
the guest bumps the length of PCI capabilities beyond the 32 byte
boundary, so the virtio-net device gets 64 bytes of ioport space
instead of 32, which offsets the address of all the other following
devices. Migration doesn't work very well when the location and length
of PCI capabilities of devices is changed between source and
destination.
This means that we need to make sure that the absence/presence of
host_mtu on the qemu commandline always matches between source and
destination, which means that we need to make setting of host_mtu an
opt-in thing (it can't happen automatically when the bridge being used
has a non-default MTU, which is what commit 2841e675 implemented).
I do want to re-implement this feature with an <mtu auto='on'/>
setting, but probably won't backport that to any stable branches, so
I'm first reverting the original commit, and that revert can be pushed
to the few releases that have been made since the original (3.1.0 -
3.3.0)
Resolves: https://bugzilla.redhat.com/1449346
libvirt was able to set the host_mtu option when an MTU was explicitly
given in the interface config (with <mtu size='n'/>), set the MTU of a
libvirt network in the network config (with the same named
subelement), and would automatically set the MTU of any tap device to
the MTU of the network.
This patch ties that all together (for networks based on tap devices
and either Linux host bridges or OVS bridges) by learning the MTU of
the network (i.e. the bridge) during qemuInterfaceBridgeConnect(), and
returning that value so that it can then be passed to
qemuBuildNicDevStr(); qemuBuildNicDevStr() then sets host_mtu in the
interface's commandline options.
The result is that a higher MTU for all guests connecting to a
particular network will be plumbed top to bottom by simply changing
the MTU of the network (in libvirt's config for libvirt-managed
networks, or directly on the bridge device for simple host bridges or
OVS bridges managed outside of libvirt).
One question I have about this - it occurred to me that in the case of
migrating a guest from a host with an older libvirt to one with a
newer libvirt, the guest may have *not* had the host_mtu option on the
older machine, but *will* have it on the newer machine. I'm curious if
this could lead to incompatibilities between source and destination (I
guess it all depends on whether or not the setting of host_mtu has a
practical effect on a guest that is already running - Maxime?)
Likewise, we could run into problems when migrating from a newer
libvirt to older libvirt - The guest would have been told of the
higher MTU on the newer libvirt, then migrated to a host that didn't
understand <mtu size='blah'/>. (If this really is a problem, it would
be a problem with or without the current patch).
If a user specify network type ethernet, then create it via libvirt and run
script if it provided. After this commit user does not need to
run external script to create tap device or add root permissions to qemu
process.
Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>
Move the misplaced function from qemu_command.c to qemu_interface.c
since it's closer in functionality there and had less to do with building
the command line.
Rename function to qemuInterfaceBridgeConnect and modify callers.
Signed-off-by: John Ferlan <jferlan@redhat.com>
Move the misplaced function from qemu_command.c to qemu_interface.c
since it's closer in functionality there and had less to do with building
the command line.
Rename function to qemuInterfaceDirectConnect and modify callers.
Signed-off-by: John Ferlan <jferlan@redhat.com>
We now have a qemuInterfaceStartDevices() which does the final
activation needed for the host-side tap/macvtap devices that are used
for qemu network connections. It will soon make sense to have the
converse qemuInterfaceStopDevices() which will undo whatever was done
during qemuInterfaceStartDevices().
A function to "stop" a single device has also been added, and is
called from the appropriate place in qemuDomainDetachNetDevice(),
although this is currently unnecessary - the device is going to
immediately be deleted anyway, so any extra "deactivation" will be for
naught. The call is included for completeness, though, in anticipation
that in the future there may be some required action that *isn't*
nullified by deleting the device.
This patch is a part of a more complete fix for:
https://bugzilla.redhat.com/show_bug.cgi?id=1081461
Currently, MAC registration occurs during device creation, which is
early enough that, during live migration, you end up with duplicate
MAC addresses on still-running source and target devices, even though
the target device isn't actually being used yet.
This patch proposes to defer MAC registration until right before
the guest can actually use the device -- In other words, right
before starting guest CPUs.
Signed-off-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
Signed-off-by: Laine Stump <laine@laine.org>
