RE: [PATCH 0/8] refactor logic to support secondary process

[Chaoyong He <chaoyong.he@corigine.com>]

> On 5/21/2024 3:17 AM, Chaoyong He wrote:
> >> On 4/19/2024 6:23 AM, Chaoyong He wrote:
> >>> Refactor data structure and related logic to make the secondary
> >>> process can work as expect.
> >>>
> >>
> >> Hi Chaoyong,
> >>
> >> Patchset looks good, but I have a question related to the motivation
> >> of moving so many structs to process private data?
> >>
> >> Normally ethdev is process private, and ethdev->data is shared.
> >> Primary configures the device and secondary learns shared data and
> >> uses it for datapath.
> >> There are cases, like file descriptors for same file can be different
> >> for different process and process private structure is used.
> >>
> >> In below patches, device private data level structs seems moved to
> >> the process private structure, is the intention both primary process
> >> and secondary process do the control path and configuration?
> >> If so, just a reminder that this is not intended usage of the
> >> multi-process support and many control APIs are not designed as thread-
> safe.
> >>
> >> Would you mind describing a little more about your use case that
> >> requires below process private data changes?
> >
> > The main motivation of these changes is to solve the problems when
> > customers using the secondary process (they use primary process for
> monitor and secondary process for rx/tx/configuration ...).
> >
> 
> Got it, if you want to do 'configuration' on the secondary, it requires more
> information, and as this is not shared you need to move them to process
> private.
> 
> This approach requires synchronizing secondaries for this control path.
> So more work for the application layer.
> 
> I understand you are trying to enable your customer, and this is a solution but
> I am not sure this is the best approach. And this solution won't be portable,
> because many PMDs won't support configuring from secondary.
> 
> Can you guide your customer that configuring on primary and limit
> secondaries for the datapath?

Sorry, but it is almost certain that it is impossible to make customer modify their architecture.
Because they have complex software stack, and they themselves are only user of the software stack.
They are just responsible for the basic NIC adaptation work and the upper software architecture are 
design and maintain by some other department.

For this generation NFP hardware and firmware architecture, seems this is the only best solution
we can achieve.

But for the next generation NIC and firmware (we already in development, and will publish in a near future),
we will have one PCI BDF address for one physical port and use a unified firmware.
Then the problems we meet for now will not exist anymore, and we can make the logic just as what you said.

> This way only some limited information is required to shared with secondaries
> (lets say like firmware application version) and these can be passed via shared
> data or even MP communication.
> 
> Although this is not a hard requirement, I believe this can make both your and
> your customer's life easier in long run.
> 
> 
> > The NFP card support different firmware applications, this means we
> > need read message from firmware to decide to run which logic.
> >
> > And with single-pf firmware (this means one PCI BDF address for multi
> > physical ports), we also need read message (how many ports totally) from
> firmware before attach to the primary process.
> >
> > All this relates with CPP and symbol table, and they are different for primary
> process and secondary process.
> > If still put them in the process shared section (ethdev->data), the
> > assignment logic in secondary process will overwrite it and cause the primary
> process crash.
> >
> > So we move them into the process private section (ethdev-
> >process_private).
> >
> 
>