[Qemu-devel] [PATCH v6 00/47] Postcopy implementation

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

  This is the 6th cut of my version of postcopy; it is designed for use with
the Linux kernel additions posted by Andrea Arcangeli here:

git clone --reference linux -b userfault18 
git://git.kernel.org/pub/scm/linux/kernel/git/andrea/aa.git

(Note this is a different API from the last version)

This qemu series can be found at:

https://github.com/orbitfp7/qemu.git
on the wp3-postcopy-v6 tag.

It addresses some but not yet all of the previous review comments;
however there are a couple of large simplifications, so it seems
worth posting to meet the new kernel API and to stop people
reviewing deadcode.

Note: That the userfaultfd.h header is no longer included in this
tree:
      - if you're building with the appropriate kernel headers it should find it
      - if you're building on a host that doesn't have the kernel headers
        installed in the right place then:
           configure with:   --extra-cflags="-D__NR_userfaultfd=323"
           cp include/uapi/linux/userfaultfd.h into somewhere in the include
           path, e.g.  /usr/local/include/linux

v6
  Removed the PMI bitmaps
      - Andrea updated the kernel API so that userspace doesn't
        need to do wakeups, and thus QEMU doesn't need to keep
        track of which pages it's received; there is a price - which
        is we end up sending more dupes to the source, but it simplifies
        stuff a lot and makes the normal paths a lot quicker.
        (10s of line change in kernel, 10%-ish simplification in this code!)
  Changed discard message format to a simpler start/end address scheme
        and rework discard and chunking code to work in long's to match bitmap
  'qemu_get_buffer_less_copy' for postcopy pages
      - avoids a userspace copy since the kernel now does it
      - the new qemufile interface might also be useful for other places that
        don't need a copy (maybe xbzrle?)
  Changed the blockingness of the incoming fd
      it was incorrectly blocking during the precopy phase after a postcopy was
      enabled, causing the HMP to be unavailable.  It's now blocking only once
      the postcopy thread starts up, since it's not a coroutine it can't deal
      with the yields in qemu_file.
  An error on the return-path now marks the migration as failed

  Fixups from Dave Gibson's comments
    Removed can_postcopy, renamed save_complete to save_complete_precopy
        added save_complete_postcopy
    Simplified loadvm loop exits
    discard message format changes above
    and many more smaller changes.

  small fixups for RCU


This work has been partially funded by the EU Orbit project:
  see http://www.orbitproject.eu/about/

TODO:
  The major work is to rework the page send/receive loops so that supporting
  larger host pages doesn't make it quite as messy.

Dr. David Alan Gilbert (47):
  Start documenting how postcopy works.
  Split header writing out of qemu_savevm_state_begin
  qemu_ram_foreach_block: pass up error value, and down the ramblock
    name
  Add qemu_get_counted_string to read a string prefixed by a count byte
  Create MigrationIncomingState
  Provide runtime Target page information
  Move copy out of qemu_peek_buffer
  Add qemu_get_buffer_less_copy to avoid copies some of the time
  Add wrapper for setting blocking status on a QEMUFile
  Rename save_live_complete to save_live_complete_precopy
  Return path: Open a return path on QEMUFile for sockets
  Return path: socket_writev_buffer: Block even on non-blocking fd's
  Migration commands
  Return path: Control commands
  Return path: Send responses from destination to source
  Return path: Source handling of return path
  ram_debug_dump_bitmap: Dump a migration bitmap as text
  Move loadvm_handlers into MigrationIncomingState
  Rework loadvm path for subloops
  Add migration-capability boolean for postcopy-ram.
  Add wrappers and handlers for sending/receiving the postcopy-ram
    migration messages.
  MIG_CMD_PACKAGED: Send a packaged chunk of migration stream
  migrate_init: Call from savevm
  Modify save_live_pending for postcopy
  postcopy: OS support test
  migrate_start_postcopy: Command to trigger transition to postcopy
  MIGRATION_STATUS_POSTCOPY_ACTIVE: Add new migration state
  Add qemu_savevm_state_complete_postcopy
  Postcopy: Maintain sentmap and calculate discard
  postcopy: Incoming initialisation
  postcopy: ram_enable_notify to switch on userfault
  Postcopy: Postcopy startup in migration thread
  Postcopy end in migration_thread
  Page request:  Add MIG_RP_MSG_REQ_PAGES reverse command
  Page request: Process incoming page request
  Page request: Consume pages off the post-copy queue
  postcopy_ram.c: place_page and helpers
  Postcopy: Use helpers to map pages during migration
  qemu_ram_block_from_host
  Don't sync dirty bitmaps in postcopy
  Host page!=target page: Cleanup bitmaps
  Postcopy; Handle userfault requests
  Start up a postcopy/listener thread ready for incoming page data
  postcopy: Wire up loadvm_postcopy_handle_ commands
  End of migration for postcopy
  Disable mlock around incoming postcopy
  Inhibit ballooning during postcopy

 arch_init.c                      | 868 ++++++++++++++++++++++++++++++++++++---
 balloon.c                        |  11 +
 docs/migration.txt               | 167 ++++++++
 exec.c                           |  74 +++-
 hmp-commands.hx                  |  15 +
 hmp.c                            |   7 +
 hmp.h                            |   1 +
 hw/ppc/spapr.c                   |   2 +-
 hw/virtio/virtio-balloon.c       |   4 +-
 include/exec/cpu-all.h           |   2 -
 include/exec/cpu-common.h        |   7 +-
 include/migration/migration.h    | 126 +++++-
 include/migration/postcopy-ram.h |  88 ++++
 include/migration/qemu-file.h    |  15 +-
 include/migration/vmstate.h      |  10 +-
 include/qemu/typedefs.h          |   5 +
 include/sysemu/balloon.h         |   2 +
 include/sysemu/sysemu.h          |  45 +-
 migration/Makefile.objs          |   2 +-
 migration/block.c                |   9 +-
 migration/migration.c            | 743 +++++++++++++++++++++++++++++++--
 migration/postcopy-ram.c         | 715 ++++++++++++++++++++++++++++++++
 migration/qemu-file-unix.c       | 106 ++++-
 migration/qemu-file.c            | 100 ++++-
 migration/rdma.c                 |   4 +-
 migration/vmstate.c              |   5 +-
 qapi-schema.json                 |  19 +-
 qmp-commands.hx                  |  19 +
 savevm.c                         | 809 ++++++++++++++++++++++++++++++++----
 trace-events                     |  77 +++-
 30 files changed, 3832 insertions(+), 225 deletions(-)
 create mode 100644 include/migration/postcopy-ram.h
 create mode 100644 migration/postcopy-ram.c

-- 
2.1.0