Re: [dpdk-dev] [PATCH v4 1/6] ethdev: add capability to keep flow rules on restart

[Ajit Khaparde <ajit.khaparde@broadcom.com>]

On Wed, Oct 20, 2021 at 11:35 PM Dmitry Kozlyuk <dkozlyuk@oss.nvidia.com> wrote:
>
> Previously, it was not specified what happens to the flow rules
> when the device is stopped, possibly reconfigured, then started.
> If flow rules were kept, it could be convenient for application
> developers, because they wouldn't need to save and restore them.
> However, due to the number of flows and possible creation rate it is
> impractical to save all flow rules in DPDK layer. This means that flow
> rules persistence really depends on whether PMD and HW can implement it
> efficiently. It can also be limited by the rule item and action types,
> and its attributes transfer bit (a combination of an item/action type
> and a value of the transfer bit is called a ruel feature).
>
> Add a device capability bit for PMDs that can keep at least some
> of the flow rules across restart. Without this capability behavior
> is still unspecified and it is declared that the application must
> flush the rules before stopping the device.
> Allow the application to test for persistence of rules using
> a particular feature by attempting to create a flow rule
> using that feature when the device is stopped
> and checking for the specific error.
> This is logical because if the PMD can to create the flow rule
> when the device is not started and use it after the start happens,
> it is natural that it can move its internal flow rule object
> to the same state when the device is stopped and restore the state
> when the device is started.
>
> Rule persistence across a reconfigurations is not required,
> because tracking all the rules and configuration-dependent resources
> they use may be infeasible. In case a PMD cannot keep the rules
> across reconfiguration, it is allowed just to report an error.
> Application must then flush the rules before attempting it.
>
> Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>

Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>