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[v3,0/8] Migration: Make misc.h helpers available for whole VM lifecycle

Message ID 20241024213056.1395400-1-peterx@redhat.com (mailing list archive)
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Series Migration: Make misc.h helpers available for whole VM lifecycle | expand

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Peter Xu Oct. 24, 2024, 9:30 p.m. UTC 
Based-on: <20241024165627.1372621-1-peterx@redhat.com>
CI:       https://gitlab.com/peterx/qemu/-/pipelines/1511349805

This is a follow up of below patch from Avihai as a replacement:

https://lore.kernel.org/qemu-devel/20241020130108.27148-3-avihaih@nvidia.com/

This is v3 of the series, and it happened again: changelog doesn't make
sense to compare to v2 because it's rewritten.  Meanwhile, now this series
is based on the other TYPE_SINGLETON series I posted just now:

https://lore.kernel.org/r/20241024165627.1372621-1-peterx@redhat.com

It turns out I found more things to cleanup, as the versions spin up.

Patch 1:     I found that object_ref() in migration thread is actually also
             racy..  this should fix it.

Patch 2-7:   It turns out I decided to clean things up first, then it'll
             make my last patch easier on adding the mutex protection for
             the current_migration reference

Patch 8:     The fix for NULL-dereference / race for the exported
             functions.  VFIO can hit it only because VFIO's specialty
             in using migration helpers in vmstate handlers, I guess.  I
             found most functions always safe because even if they're used
             outside migration/ they're most likely still invoked with
             migration thread context.  So I found only two functions that
             really need protections, exactly what VFIO is using.

Comments welcomed, thanks.

Peter Xu (8):
  migration: Take migration object refcount earlier for threads
  migration: Unexport dirty_bitmap_mig_init()
  migration: Unexport ram_mig_init()
  migration: Drop migration_is_setup_or_active()
  migration: Drop migration_is_idle()
  migration: Drop migration_is_device()
  migration: Unexport migration_is_active()
  migration: Protect updates to current_migration with a mutex

 include/migration/misc.h |  11 +---
 migration/migration.h    |   8 +++
 migration/ram.h          |   1 +
 hw/vfio/common.c         |   6 +-
 hw/virtio/virtio-mem.c   |   2 +-
 migration/migration.c    | 118 +++++++++++++++++++--------------------
 migration/ram.c          |   7 +--
 net/vhost-vdpa.c         |   3 +-
 system/dirtylimit.c      |   3 +-
 system/qdev-monitor.c    |   4 +-
 10 files changed, 81 insertions(+), 82 deletions(-)