From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

Dear friends,

This patchset adds basic live migration support for
QEMU emulated NVMe device.

Implementation has some limitations:
- only one NVMe namespace is supported
- SMART counters are not preserved
- CMB is not supported
- PMR is not supported
- SPDM is not supported
- SR-IOV is not supported

I believe this is something I can support in next patchset versions or
separately on-demand (when usecase appears).

Testing.

This patch series was manually tested on:
- Debian 13.3 VM (kernel 6.12.69+deb13-amd64) using fio on *non-root* NVMe disk
  (root disk was virtio-scsi):

time fio --name=nvme-verify \
    --filename=/dev/nvme0n1 \
    --size=5G \
    --rw=randwrite \
    --bs=4k \
    --iodepth=16 \
    --numjobs=1 \
    --direct=0 \
    --ioengine=io_uring \
    --verify=crc32c \
    --verify_fatal=1

- Windows Server 2022 VM (NVMe drive was a *root* disk) with opened browser
  playing video.

No defects were found.

Git tree:
https://github.com/mihalicyn/qemu/commits/nvme-live-migration

Changelog for version 6:
- rebased on top of:
  https://gitlab.com/peterx/qemu/-/tree/vmstate-array-null
  (see also https://lore.kernel.org/all/20260401202844.673494-1-peterx@redhat.com)
- addressed review comments from Stefan Hajnoczi:
  - supported "full CQ" case by serializing NvmeRequest state
  - added qtest for NVMe device migration with full CQ

Changelog for version 5:
- rebased on top of https://lore.kernel.org/all/20260304212303.667141-1-vsementsov@yandex-team.ru/
  (as Peter has requested)

Changelog for version 4:
- vmstate dynamic array support reworked as suggested by Peter Xu
  VMS_ARRAY_OF_POINTER_ALLOW_NULL flag was introduced
  qtests were added
- NVMe migration blockers were reworked as Klaus has requested earlier
  Now, instead of having "deny list" approach, we have more strict pattern
  of NVMe features filtering and it should be harded to break migration when
  adding new NVMe features.

Changelog for version 3:
- rebased
- simple functional test was added (in accordance with Klaus Jensen's review comment)
  $ meson test 'func-x86_64-nvme_migration' --setup thorough -C build

Changelog for version 2:
- full support for AERs (in-flight requests and queued events too)

Kind regards,
Alex

Alexander Mikhalitsyn (8):
  tests/functional/migration: add VM launch/configure hooks
  hw/nvme: add migration blockers for non-supported cases
  hw/nvme: split nvme_init_sq/nvme_init_cq into helpers
  hw/nvme: set CQE.sq_id earlier in nvme_process_sq
  hw/nvme: unmap req->sg earlier in nvme_enqueue_req_completion
  hw/nvme: add basic live migration support
  tests/functional/x86_64: add migration test for NVMe device
  tests/qtest/nvme-test: add migration test with full CQ

 hw/nvme/ctrl.c                                | 992 +++++++++++++++++-
 hw/nvme/ns.c                                  | 160 +++
 hw/nvme/nvme.h                                |  12 +
 hw/nvme/trace-events                          |  10 +
 include/block/nvme.h                          |  12 +
 tests/functional/migration.py                 |  22 +-
 tests/functional/x86_64/meson.build           |   1 +
 .../functional/x86_64/test_nvme_migration.py  | 159 +++
 tests/qtest/nvme-test.c                       | 393 +++++++
 9 files changed, 1725 insertions(+), 36 deletions(-)
 create mode 100755 tests/functional/x86_64/test_nvme_migration.py

-- 
2.47.3