[PATCH v4 2/3] ethdev: add standby state for live migration

[Jerin Jacob]

On Wed, Jan 18, 2023 at 9:15 PM Rongwei Liu <rongweil at nvidia.com> wrote:
>
> When a DPDK application must be upgraded,
> the traffic downtime should be shortened as much as possible.
> During the migration time, the old application may stay alive
> while the new application is starting and being configured.
>
> In order to optimize the switch to the new application,
> the old application may need to be aware of the presence
> of the new application being prepared.
> This is achieved with a new API allowing the user to change the
> new application state to standby and active later.
>
> The added function is trying to apply the new state to all probed
> ethdev ports. To make this API simple and easy to use,
> the same flags have to be accepted by all devices.
>
> This is the scenario of operations in the old and new applications:
> .       device: already configured by the old application
> .       new:    start as active
> .       new:    probe the same device

How to probe same device if is already bind to another application?
vfio-pci wont allow this.

Good to see any implementation and example application to exercise this APIs


> .       new:    set as standby
> .       new:    configure the device
> .       device: has configurations from old and new applications
> .       old:    clear its device configuration
> .       device: has only 1 configuration from new application
> .       new:    set as active
> .       device: downtime for connecting all to the new application
> .       old:    shutdown
>
> The active role means network handling configurations are programmed
> to the HW immediately, and no behavior changed. This is the default state.
> The standby role means configurations are queued in the HW.
> If there is no application with active role,
> any configuration is effective immediately.
>
> Signed-off-by: Rongwei Liu <rongweil at nvidia.com>