[Qemu-devel] [RFC PATCH 00/17] COarse-grain LOck-stepping(COLO) Virtual Machines for Non-stop Service

[Yang Hongyang]

Virtual machine (VM) replication is a well known technique for
providing application-agnostic software-implemented hardware fault
tolerance "non-stop service". COLO is a high availability solution.
Both primary VM (PVM) and secondary VM (SVM) run in parallel. They
receive the same request from client, and generate response in parallel
too. If the response packets from PVM and SVM are identical, they are
released immediately. Otherwise, a VM checkpoint (on demand) is
conducted. The idea is presented in Xen summit 2012, and 2013,
and academia paper in SOCC 2013. It's also presented in KVM forum
2013:
http://www.linux-kvm.org/wiki/images/1/1d/Kvm-forum-2013-COLO.pdf
Please refer to above document for detailed information. 
Please also refer to previous posted RFC proposal:
http://lists.nongnu.org/archive/html/qemu-devel/2014-06/msg05567.html

The patchset is also hosted on github:
https://github.com/macrosheep/qemu/tree/colo_v0.1

This patchset is RFC, implements the frame of colo, without
failover and nic/disk replication. But it is ready for demo
the COLO idea above QEMU-Kvm.
Steps using this patchset to get an overview of COLO:
1. configure the source with --enable-colo option
2. compile
3. just like QEMU's normal migration, run 2 QEMU VM:
   - Primary VM 
   - Secondary VM with -incoming tcp:[IP]:[PORT] option
4. on Primary VM's QEMU monitor, run following command:
   migrate_set_capability colo on
   migrate tcp:[IP]:[PORT]
5. done
you will see two runing VMs, whenever you make changes to PVM, SVM
will be synced to PVM's state.

TODO list:
1. failover
2. nic replication
3. disk replication[COLO Disk manager]

Any comments/feedbacks are warmly welcomed.

Thanks,
Yang

Yang Hongyang (17):
  configure: add CONFIG_COLO to switch COLO support
  COLO: introduce an api colo_supported() to indicate COLO support
  COLO migration: add a migration capability 'colo'
  COLO info: use colo info to tell migration target colo is enabled
  COLO save: integrate COLO checkpointed save into qemu migration
  COLO restore: integrate COLO checkpointed restore into qemu restore
  COLO buffer: implement colo buffer as well as QEMUFileOps based on it
  COLO: disable qdev hotplug
  COLO ctl: implement API's that communicate with colo agent
  COLO ctl: introduce is_slave() and is_master()
  COLO ctl: implement colo checkpoint protocol
  COLO ctl: add a RunState RUN_STATE_COLO
  COLO ctl: implement colo save
  COLO ctl: implement colo restore
  COLO save: reuse migration bitmap under colo checkpoint
  COLO ram cache: implement colo ram cache on slaver
  HACK: trigger checkpoint every 500ms

 Makefile.objs                      |   2 +
 arch_init.c                        | 174 +++++++++-
 configure                          |  14 +
 include/exec/cpu-all.h             |   1 +
 include/migration/migration-colo.h |  36 +++
 include/migration/migration.h      |  13 +
 include/qapi/qmp/qerror.h          |   3 +
 migration-colo-comm.c              |  78 +++++
 migration-colo.c                   | 643 +++++++++++++++++++++++++++++++++++++
 migration.c                        |  45 ++-
 qapi-schema.json                   |   9 +-
 stubs/Makefile.objs                |   1 +
 stubs/migration-colo.c             |  34 ++
 vl.c                               |  12 +
 14 files changed, 1044 insertions(+), 21 deletions(-)
 create mode 100644 include/migration/migration-colo.h
 create mode 100644 migration-colo-comm.c
 create mode 100644 migration-colo.c
 create mode 100644 stubs/migration-colo.c

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1.9.1