Re: [dpdk-dev] [PATCH v4 0/6] Flow entites behavior on port restart

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 10/21/2021 7:34 AM, Dmitry Kozlyuk wrote:
> It is unspecified whether flow rules and indirect actions are kept
> when a port is stopped, possibly reconfigured, and started again.
> Vendors approach the topic differently, e.g. mlx5 and i40e PMD
> disagree in whether flow rules can be kept, and mlx5 PMD would keep
> indirect actions. In the end, applications are greatly affected
> by whatever contract there is and need to know it.
> 
> Applications may wish to restart the port to reconfigure it,
> e.g. switch offloads or even modify queues.
> Keeping rte_flow entities enables application improvements:
> 1. Since keeping the rules across restart comes with the ability
>     to create rules before the device is started. This allows
>     to have all the rules created at the moment of start,
>     so that there is no time frame when traffic is coming already,
>     but the rules are not yet created (restored).
> 2. When a rule or an indirect action has some associated state,
>     such as a counter, application saves the need to keep
>     additional state in order to cope with information loss
>     if such an entity would be destroyed.
> 
> It is proposed to advertise capabilities of keeping flow rules
> and indirect actions (as a special case of shared object)
> using a combination of ethdev info and rte_flow calls.
> Then a bug is fixed in mlx5 PMD that prevented indirect RSS action
> from being kept, and the driver starts advertising the new capability.
> 
> Prior discussions:
> 1) http://inbox.dpdk.org/dev/20210727073121.895620-1-dkozlyuk@nvidia.com/
> 2) http://inbox.dpdk.org/dev/20210901085516.3647814-1-dkozlyuk@nvidia.com/
> 
> v4:  1. Fix rebase conflicts (CI).
>       2. State rule behavior when a port is not started or stopped (Ori).
>       3. Improve wording on rule features, add examples (Andrew).
>       4. State that rules/actions that cannot be kept while other can be
>          must be destroyed by the application (Andrew/Ori).
>       5. Add rationale to the cover letter (Andrew).
> 
> Dmitry Kozlyuk (6):
>    ethdev: add capability to keep flow rules on restart
>    ethdev: add capability to keep shared objects on restart
>    net: advertise no support for keeping flow rules
>    net/mlx5: discover max flow priority using DevX
>    net/mlx5: create drop queue using DevX
>    net/mlx5: preserve indirect actions on restart
> 

Requesting review from PMD maintainers.

Since this patch tries to define behavior on keeping/flushing flow rules
after port stop/start/configure, better to get more feedback from various
vendors, please review/comment on patch so that we can get it for -rc2.

If there is no comment the patch can go in as it is for -rc2.

Thanks,
ferruh