Re: [RFC v3 2/2] ethdev: add API to set process to active or standby

[Jerin Jacob <jerinjacobk@gmail.com>]

On Wed, Dec 21, 2022 at 3:02 PM Rongwei Liu <rongweil@nvidia.com> wrote:
>
> HI Jerin:
>

Hi Rongwei

> BR
> Rongwei
>
> > -----Original Message-----
> > From: Jerin Jacob <jerinjacobk@gmail.com>
> > Sent: Wednesday, December 21, 2022 17:13
> > To: Rongwei Liu <rongweil@nvidia.com>
> > Cc: Matan Azrad <matan@nvidia.com>; Slava Ovsiienko
> > <viacheslavo@nvidia.com>; Ori Kam <orika@nvidia.com>; NBU-Contact-
> > Thomas Monjalon (EXTERNAL) <thomas@monjalon.net>; Ferruh Yigit
> > <ferruh.yigit@amd.com>; Andrew Rybchenko
> > <andrew.rybchenko@oktetlabs.ru>; dev@dpdk.org; Raslan Darawsheh
> > <rasland@nvidia.com>
> > Subject: Re: [RFC v3 2/2] ethdev: add API to set process to active or standby
> >
> > External email: Use caution opening links or attachments
> >
> >
> > On Wed, Dec 21, 2022 at 2:31 PM Rongwei Liu <rongweil@nvidia.com> wrote:
> > >
> > > Users may want to change the DPDK process to different versions
> >
> > Different version of DPDK? If there is any ABI change how to support this?
> >
> There is a new member which was introduced into rte_eth_dev_info but it shouldn’t be ABI breaking since using reserved fields.

That is just for rte_eth_dev_info. What about the ABI change in
different ethdev structure and rte_flow structures across different
DPDK ABI versions.

> > > such as hot upgrade.
> > > There is a strong requirement to simplify the logic and shorten the
> > > traffic downtime as much as possible.
> > >
> > > This update introduces new rte_eth process role definitions: active or
> > > standby.
> > >
> > > The active role means rules are programmed to HW immediately, and no
> >
> > Why it has to be specific only to rte_flow rule? If it spedieic to rte_flow, why it
> > is in rte_eth_process_ name space?
> For now, this design focuses on the flow rule offloading and traffic redirection.
> When switching process version, it' important to make sure which application receives and handles the traffic.

Changing the DPDK version runtime is just beyond rte_flow driver.

> The changing should be effective across all probing eth devices, that' why it was put under rte_eth_process_ (for all rte_eth_dev) name space.
> >
> > Also, if we are moving the standby, What about the rule whose ABI is changed
> > between versions?
>
> Like the comments mentioned: " Before role transition, all the rules set by the active process should be flushed first. "

What happens to rte_flow flow handles for existing ones  which is
created with version X?
Also What if new version Y has ABI change in rte_flow_pattern and
rte_flow_action structure?

For me, If DPDK version change is needed, simply reload the
application. This API will soon bloat, and it will be a mess if to
start handling
Different DPDK version which is not ABI compatible at all.




> > > behavior changed. This is the default state.
> > > The standby role means rules are queued in the HW. If no active roles
> > > alive or back to active, the rules are effective immediately.
> > >
> > > Signed-off-by: Rongwei Liu <rongweil@nvidia.com>