Re: [PATCH v2 00/11] vfio/migration: Implement VFIO migration protocol v2

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 7 Jun 2022 20:44:23 +0300
Avihai Horon <avihaih@nvidia.com> wrote:

> On 5/30/2022 8:07 PM, Avihai Horon wrote:
> > Hello,
> >
> > Following VFIO migration protocol v2 acceptance in kernel, this series
> > implements VFIO migration according to the new v2 protocol and replaces
> > the now deprecated v1 implementation.
> >
> > The main differences between v1 and v2 migration protocols are:
> > 1. VFIO device state is represented as a finite state machine instead of
> >     a bitmap.
> >
> > 2. The migration interface with kernel is done using VFIO_DEVICE_FEATURE
> >     ioctl and normal read() and write() instead of the migration region
> >     used in v1.
> >
> > 3. Migration protocol v2 currently doesn't support the pre-copy phase of
> >     migration.
> >
> > Full description of the v2 protocol and the differences from v1 can be
> > found here [1].
> >
> > Patches 1-3 are prep patches fixing bugs and adding QEMUFile function
> > that will be used later.
> >
> > Patches 4-6 refactor v1 protocol code to make it easier to add v2
> > protocol.
> >
> > Patches 7-11 implement v2 protocol and remove v1 protocol.
> >
> > Thanks.
> >
> > [1]
> > https://lore.kernel.org/all/20220224142024.147653-10-yishaih@nvidia.com/
> >
> > Changes from v1: https://lore.kernel.org/all/20220512154320.19697-1-avihaih@nvidia.com/
> > - Split the big patch that replaced v1 with v2 into several patches as
> >    suggested by Joao, to make review easier.
> > - Change warn_report to warn_report_once when container doesn't support
> >    dirty tracking.
> > - Add Reviewed-by tag.
> >
> > Avihai Horon (11):
> >    vfio/migration: Fix NULL pointer dereference bug
> >    vfio/migration: Skip pre-copy if dirty page tracking is not supported
> >    migration/qemu-file: Add qemu_file_get_to_fd()
> >    vfio/common: Change vfio_devices_all_running_and_saving() logic to
> >      equivalent one
> >    vfio/migration: Move migration v1 logic to vfio_migration_init()
> >    vfio/migration: Rename functions/structs related to v1 protocol
> >    vfio/migration: Implement VFIO migration protocol v2
> >    vfio/migration: Remove VFIO migration protocol v1
> >    vfio/migration: Reset device if setting recover state fails
> >    vfio: Alphabetize migration section of VFIO trace-events file
> >    docs/devel: Align vfio-migration docs to VFIO migration v2
> >
> >   docs/devel/vfio-migration.rst |  77 ++--
> >   hw/vfio/common.c              |  21 +-
> >   hw/vfio/migration.c           | 640 ++++++++--------------------------
> >   hw/vfio/trace-events          |  25 +-
> >   include/hw/vfio/vfio-common.h |   8 +-
> >   migration/migration.c         |   5 +
> >   migration/migration.h         |   3 +
> >   migration/qemu-file.c         |  34 ++
> >   migration/qemu-file.h         |   1 +
> >   9 files changed, 252 insertions(+), 562 deletions(-)
> >  
> Ping.

Based on the changelog, this seems like a mostly cosmetic spin and I
don't see that all of the discussion threads from v1 were resolved to
everyone's satisfaction.  I'm certainly still uncomfortable with the
pre-copy behavior and I thought there were still some action items to
figure out whether an SLA is present and vet the solution with
management tools.  Thanks,

Alex