Re: [PATCH v2 1/1] docs/devel: Add VFIO device migration documentation

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Mar 11, 2021 at 12:50:09AM +0530, Tarun Gupta wrote:
> Document interfaces used for VFIO device migration. Added flow of state changes
> during live migration with VFIO device. Tested by building docs with the new
> vfio-migration.rst file.
> 
> v2:
> - Included the new vfio-migration.rst file in index.rst
> - Updated dirty page tracking section, also added details about
>   'pre-copy-dirty-page-tracking' opt-out option.
> - Incorporated comments around wording of doc.
> 
> Signed-off-by: Tarun Gupta <targupta@nvidia.com>
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> ---
>  MAINTAINERS                   |   1 +
>  docs/devel/index.rst          |   1 +
>  docs/devel/vfio-migration.rst | 135 ++++++++++++++++++++++++++++++++++
>  3 files changed, 137 insertions(+)
>  create mode 100644 docs/devel/vfio-migration.rst


> +Postcopy
> +========
> +
> +Postcopy migration is not supported for VFIO devices.

What is the problem here and is there any plan for how to address it ?

Postcopy is essentially the only migration mechanism that can reliably
complete, so it really should be considered the default approach to
migration for all mgmt apps wanting to do migration, except in special
cases.   IOW, if we want VFIO migration to be viable, we need postcopy
support.


Regards,
Daniel
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