[PATCH v3 0/9] migration: Fix issues during qmp_migrate_cancel

[Fabiano Rosas <farosas@suse.de>]

changes from v2:

Added more if != CANCELLING where it was missing. We have other work
[1] pending around migration states, so I've kept this simple for
correctness only.

CI run: https://gitlab.com/farosas/qemu/-/pipelines/1670135398

1- https://lore.kernel.org/r/20250110100707.4805-1-shivam.kumar1@nutanix.com

v2:
https://lore.kernel.org/r/20250211150136.6781-1-farosas@suse.de
v1:
https://lore.kernel.org/r/20241202220137.32584-1-farosas@suse.de

While working on downstream issues with postcopy, I ended up writing a
set of tests for issuing qmp_migrate_cancel() at various points during
the migration. That exposed some bugs, which this series attempts to
fix.

There is also a fix for the issue Daniel found:

https://gitlab.com/qemu-project/qemu/-/issues/2633

I'm also sending the test code. It creates one test per
MIGRATION_STATUS_ state. Each test starts a migration, waits for that
specific state to be reached, issues qmp_migrate_cancel() and checks
that the migration state changes to cancelled (for now only cancelling
migration from the source side).

I was initially worried that this would be too racy, but so far each
test has survived 1000 iterations. I'm thinking it's worth merging,
specially because even after working on this I haven't been able to
clear the questions we have in our todo list [1], so we'll probably
need more work around this area in the future.

1- https://wiki.qemu.org/ToDo/LiveMigration#Migration_cancel_concurrency

Fabiano Rosas (9):
  migration: Set migration error outside of migrate_cancel
  migration: Unify migration_cancel and migrate_fd_cancel
  migration: Change migrate_fd_ to migration_
  migration: Fix hang after error in destination setup phase
  migration: Reject qmp_migrate_cancel after postcopy
  migration: Don't set FAILED state when cancelling
  tests/qtest/migration: Introduce migration_test_add_suffix
  tests/qtest/migration: Add a cancel test
  migration: Update migrate_cancel documentation

 migration/channel.c                    |   9 +-
 migration/migration.c                  |  81 +++++++-----
 migration/migration.h                  |   4 +-
 migration/multifd.c                    |   2 +-
 migration/ram.c                        |   4 +-
 migration/rdma.c                       |   2 +-
 migration/trace-events                 |   4 +-
 qapi/migration.json                    |   4 +-
 tests/qtest/migration/migration-util.c |  24 ++++
 tests/qtest/migration/migration-util.h |   2 +
 tests/qtest/migration/precopy-tests.c  | 176 +++++++++++++++++++++++++
 11 files changed, 267 insertions(+), 45 deletions(-)

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2.35.3