On Wed, May 13, 2015 at 10:30:32AM -0400, Laine Stump wrote:
> On 05/13/2015 05:57 AM, Daniel P. Berrange wrote:
> > On Wed, May 13, 2015 at 11:36:30AM +0800, Chen Fan wrote:
> >> add migration support for ephemeral host devices, introduce
> >> two 'detach' and 'restore' functions to unplug/plug host devices
> >> during migration.
> >>
> >> Signed-off-by: Chen Fan <chen.fan.fnst@xxxxxxxxxxxxxx>
> >> ---
> >> src/qemu/qemu_migration.c | 171 ++++++++++++++++++++++++++++++++++++++++++++--
> >> src/qemu/qemu_migration.h | 9 +++
> >> src/qemu/qemu_process.c | 11 +++
> >> 3 files changed, 187 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
> >> index 56112f9..d5a698f 100644
> >> --- a/src/qemu/qemu_migration.c
> >> +++ b/src/qemu/qemu_migration.c
> >
> >> +void
> >> +qemuMigrationRestoreEphemeralDevices(virQEMUDriverPtr driver,
> >> + virConnectPtr conn,
> >> + virDomainObjPtr vm,
> >> + bool live)
> >> +{
> >> + qemuDomainObjPrivatePtr priv = vm->privateData;
> >> + virDomainDeviceDefPtr dev;
> >> + int ret = -1;
> >> + size_t i;
> >> +
> >> + VIR_DEBUG("Rum domain restore ephemeral devices");
> >> +
> >> + for (i = 0; i < priv->nEphemeralDevices; i++) {
> >> + dev = priv->ephemeralDevices[i];
> >> +
> >> + switch ((virDomainDeviceType) dev->type) {
> >> + case VIR_DOMAIN_DEVICE_NET:
> >> + if (live) {
> >> + ret = qemuDomainAttachNetDevice(conn, driver, vm,
> >> + dev->data.net);
> >> + } else {
> >> + ret = virDomainNetInsert(vm->def, dev->data.net);
> >> + }
> >> +
> >> + if (!ret)
> >> + dev->data.net = NULL;
> >> + break;
> >> + case VIR_DOMAIN_DEVICE_HOSTDEV:
> >> + if (live) {
> >> + ret = qemuDomainAttachHostDevice(conn, driver, vm,
> >> + dev->data.hostdev);
> >> + } else {
> >> + ret =virDomainHostdevInsert(vm->def, dev->data.hostdev);
> >> + }
> >
> > This re-attach step is where we actually have far far far worse problems
> > than with detach. This is blindly assuming that the guest on the target
> > host can use the same hostdev that it was using on the source host.
>
> (kind of pointless to comment on, since pkrempa has changed my opinion
> by forcing me to think about the "failure to reattach" condition, but
> could be useful info for others)
>
> For a <hostdev>, yes, but not for <interface type='network'> (which
> would point to a libvirt network pool of VFs).
I should note that in OpenStack at least we don't ever use the
libvirt <interface type='network'> feature. This is because the
OpenStack scheduler needs to have better control over exactly
which VFs are allocated to which guest. This code runs on a
separate host, and takes into account stuff such as the NUMA
affinity of the guest, the utilization of the VFs by other
guests, and more besides. So even in the <interface> case
this proposal is pretty limited in usefulness.
Regards,
Daniel
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