On 05/23/2017 02:52 PM, Daniel Henrique Barboza wrote:
Hi Laurent,
This is an interesting patch series. I've been working in the last
weeks in the DRC
migration, mainly to solve the problem in which a hot CPU unplug will
not succeed after
a migration if the CPU was hotplugged in the source. The problem
happened when
migrating with virsh because Libvirt hotplugs the CPU in both source
and target, and
the DRC state of the hotplugged after the migration is inconsistent.
This series solves the
issue by preventing it from happening in the first place. Of course
that migrating DRC states
has other uses (pending unplug operations during a migration, for
example) so both patch
series can coexist.
One possible issue I see with this series is that it breaks Libvirt
migration entirely if
a CPU/mem hotplug happens in the target. With your series applied the
migration
fails before start with:
Sorry: if a migration happens in the *source*, before the migration.
# ./virsh -c 'qemu:///system' migrate --live --domain dhb_ub1704_nfs
--desturi qemu+ssh://target_ip/system --timeout 60 --verbose
error: internal error: unable to execute QEMU command 'device_add':
CPU hotplug not supported without OS
Note that I say "possible issue" because, although I believe we do not
want to break Libvirt
if possible, I also believe that we need to think about what makes
sense in QEMU first.
Thanks,
Daniel
On 05/23/2017 08:18 AM, Laurent Vivier wrote:
If the OS is not started, QEMU sends an event to the OS
that is lost and cannot be recovered. An unplug is not
able to restore QEMU in a coherent state.
So, while the OS is not started, disable CPU and memory hotplug.
We use option vector 6 to know if the OS is started
This series moves error checking for memory hotplug
in a pre_plug function, and introduces the option
vector 6 management. It also revert previous
fix which was not really fixing the hotplug problem
when the OS is not running.
Laurent Vivier (4):
spapr: add pre_plug function for memory
spapr: add option vector 6
spapr: disable hotplugging without OS
Revert "spapr: fix memory hot-unplugging"
hw/ppc/spapr.c | 103
++++++++++++++++++++++++++++++++++++--------
hw/ppc/spapr_drc.c | 20 ++-------
hw/ppc/spapr_hcall.c | 5 ++-
hw/ppc/spapr_ovec.c | 8 ++++
include/hw/ppc/spapr.h | 2 +
include/hw/ppc/spapr_drc.h | 1 -
include/hw/ppc/spapr_ovec.h | 7 +++
7 files changed, 109 insertions(+), 37 deletions(-)