Re: [PATCH v3 0/5] scsi: persistent reservation live migration

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Thu, Jan 29, 2026 at 04:20:30PM -0500, Stefan Hajnoczi wrote:
> v3:
> - Use warn_report_err() instead of suppressing errors [Daniel Berrangé]
> - Wrap lines exceeding 80 characters
> 
> v2:
> - Add user documentation [Paolo]
> - Send PREEMPT on the source if migration fails. This rollback operation
>   ensures the source regains access to the LUN even if migration fails after
>   the destination issues its own PREEMPT.
> 
> Live migration does not work for SCSI Persistent Reservations acquired on
> scsi-block devices. This patch series migrates the reservation key and
> reservation type so that the destination QEMU can take over the persistent
> reservation with the PREEMPT service action upon live migration.
> 
> The approach involves snooping PERSISTENT RESERVE OUT replies and tracking the
> scsi-block device's current reservation key and reservation type. In most cases
> this involves no additional SCSI commands. This approach isn't perfect: if
> another machine modifies the reservation on the physical LUN, then QEMU's state
> becomes stale. Persistent reservations are inherently cooperative, so this is
> acceptable as long as real applications don't run into problems.
> 
> I am also working on a test suite called pr-tests that runs sg_persist(8)
> commands across multiple machines in order to exercise various scenarios:
> https://gitlab.com/stefanha/pr-tests
> 
> Stefan Hajnoczi (5):
>   scsi: generalize scsi_SG_IO_FROM_DEV() to scsi_SG_IO()
>   scsi: add error reporting to scsi_SG_IO()
>   scsi: track SCSI reservation state for live migration
>   scsi: save/load SCSI reservation state
>   docs: add SCSI migrate-pr documentation
> 
>  docs/system/device-emulation.rst        |   1 +
>  docs/system/devices/scsi/index.rst      |  10 +
>  docs/system/devices/scsi/migrate-pr.rst |  54 +++++
>  include/hw/scsi/scsi.h                  |  15 +-
>  include/scsi/constants.h                |  21 ++
>  hw/core/machine.c                       |   4 +-
>  hw/scsi/scsi-bus.c                      |   3 +
>  hw/scsi/scsi-disk.c                     |  90 +++++++-
>  hw/scsi/scsi-generic.c                  | 291 +++++++++++++++++++++++-
>  hw/scsi/trace-events                    |   2 +
>  10 files changed, 476 insertions(+), 15 deletions(-)
>  create mode 100644 docs/system/devices/scsi/index.rst
>  create mode 100644 docs/system/devices/scsi/migrate-pr.rst
> 
> -- 
> 2.52.0
> 

Thanks, applied to my block tree:
https://gitlab.com/stefanha/qemu/commits/block

Stefan

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