From: Michael Roth <mdroth@linux.vnet.ibm.com>
To: qemu-devel@nongnu.org
Cc: qemu-ppc@nongnu.org, david@gibson.dropbear.id.au,
duanj@linux.vnet.ibm.com, bharata@linux.vnet.ibm.com,
dgilbert@redhat.com, quintela@redhat.com, amit.shah@redhat.com
Subject: [Qemu-devel] [PATCH for-2.8 0/3] spapr: fix breakage of memory unplug after migration
Date: Thu, 17 Nov 2016 19:40:24 -0600 [thread overview]
Message-ID: <1479433227-29238-1-git-send-email-mdroth@linux.vnet.ibm.com> (raw)
These patches are based on David's ppc-for-2.8 tree, and are also
available from:
https://github.com/mdroth/qemu/commits/spapr-cas-migration
Currently, memory hotplugged to a pseries guest cannot be removed after
the guest has been migrated. This is due to 2 issues:
1) The coldplugged state of memory on the target side is one where the
corresponding DRC's allocation state is:
allocation_state == unallocated,
awaiting_allocation == true,
When the guest attempts to unplug memory on the target side, it first
checks that allocation_state == allocated. If we fix this, the guest
can successfully notify QEMU of completion on it's end, but then the
DRC code sees that awaiting_allocation == true, so it defers the
finalizing of the LMB and corresponding DIMM since it assumes that
the DIMM must have been previously allocated before it can be removed.
To address this, we pull in patches 1-2 from Jian Jun's DRC migration
series:
https://lists.gnu.org/archive/html/qemu-ppc/2016-10/msg00048.html
with some minor changes relating to prior review comments, and
the addition of migrating the DRC's awaiting_allocation value, which
wasn't part of the original patch. This doesn't address the full scope
of the issues Jian Jun was looking at (involving synchronizing state
when migration occurs during fairly small race windows), just this
particular case, which is more user visible since the time window is
indefinite.
2) The ability to unplug memory is gated on the QEMU side by a check as
to whether or not support for newer-style hotplug events was negotiated
via CAS during boot. The check is performed by checking the corresponding
entry in the sPAPROptionVector structure. However, since this value isn't
migrated currently, we are unable to unplug until after the guest reboots.
We address that here by adding migration support for sPAPROptionVectors,
and including the CAS-negotiated vector as part of the migration stream
for any cases where we advertise newer-style hotplug event support to
the guest.
David,
These fixes ended up going out much later than planned. I'm not sure
if you're planning another pull for 2.8 or not, and realize there are
some patches here not specifically pseries-related so it's
understandable if we opt to pursue these for 2.9/2.8.1 instead. But if
possible I'm hoping to get these in so that the memory unplug
support is fully functional for 2.8.
hw/core/qdev.c | 6 +++++-
hw/ppc/spapr.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
hw/ppc/spapr_drc.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
hw/ppc/spapr_ovec.c | 12 ++++++++++++
hw/ppc/spapr_pci.c | 22 ++++++++++++++++++++++
include/hw/ppc/spapr_drc.h | 9 +++++++++
include/hw/ppc/spapr_ovec.h | 4 ++++
include/hw/qdev-core.h | 9 +++++++++
migration/savevm.c | 4 ++--
9 files changed, 201 insertions(+), 3 deletions(-)
next reply other threads:[~2016-11-18 1:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-18 1:40 Michael Roth [this message]
2016-11-18 1:40 ` [Qemu-devel] [PATCH for-2.8 1/3] migration: alternative way to set instance_id in SaveStateEntry Michael Roth
2016-11-22 6:15 ` David Gibson
2016-11-22 10:23 ` Dr. David Alan Gilbert
2016-11-22 22:58 ` Michael Roth
2016-11-30 22:22 ` Michael Roth
2016-11-18 1:40 ` [Qemu-devel] [PATCH for-2.8 2/3] migration: spapr_drc: defined VMStateDescription struct Michael Roth
2016-11-18 6:04 ` David Gibson
2016-11-18 16:32 ` Michael Roth
2016-11-22 16:35 ` [Qemu-devel] [Qemu-ppc] " Greg Kurz
2016-11-22 17:24 ` Michael Roth
2016-11-22 17:33 ` Michael Roth
2016-11-22 21:28 ` Greg Kurz
2016-11-22 20:09 ` Greg Kurz
2016-11-18 1:40 ` [Qemu-devel] [PATCH for-2.8 3/3] spapr: migration support for CAS-negotiated option vectors Michael Roth
2016-11-18 16:08 ` Michael Roth
2016-11-20 23:57 ` David Gibson
2016-11-18 1:51 ` [Qemu-devel] [PATCH for-2.8 0/3] spapr: fix breakage of memory unplug after migration no-reply
2016-11-18 5:45 ` David Gibson
2016-11-18 16:39 ` Michael Roth
2016-11-20 23:58 ` David Gibson
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