netdev - Re: SRIOV switchdev mode BoF minutes

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Message-ID: <20180418151529.GL33938@C02RW35GFVH8.dhcp.broadcom.net>
Date:   Wed, 18 Apr 2018 11:15:29 -0400
From:   Andy Gospodarek <andrew.gospodarek@...adcom.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Andy Gospodarek <andrew.gospodarek@...adcom.com>,
        Or Gerlitz <gerlitz.or@...il.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        David Miller <davem@...emloft.net>,
        Anjali Singhai Jain <anjali.singhai@...el.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Simon Horman <simon.horman@...ronome.com>,
        John Fastabend <john.fastabend@...il.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Rony Efraim <ronye@...lanox.com>,
        Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: SRIOV switchdev mode BoF minutes

On Tue, Apr 17, 2018 at 04:19:15PM -0700, Jakub Kicinski wrote:
> On Tue, 17 Apr 2018 10:47:00 -0400, Andy Gospodarek wrote:
> > There is also a school of thought that the VF reps could be
> > pre-allocated on the SmartNIC so that any application processing that
> > traffic would sit idle when no traffic arrives on the rep, but could
> > process frames that do arrive when the VFs were created on the host.
> > This implementation will depend on how resources are allocated on a
> > given bit of hardware, but can really work well.
> 
> +1 if there is no FW resource allocation issues IMHO it's okay to
> just show all reprs for "remote PCIes (PFs and VFs)" on the SmartNIC/
> controller.  The reprs should just show link down as if PCIe cable
> was unpluged until host actually enables them.  

Yes we are on the same page on this.

> A similar issue exists on multi-host for PFs, right?  If one of the
> hosts is down do we still show their PF repr?  IMHO yes.

I would agree with that as well.  With today's model the VF reps are
created once a PF is put into switchdev mode, but I'm still working out
how we want to consider whether or not a PF rep for the other domains is
created locally or not and also how one can determine which domain is in
control.

Permanent config options (like NVRAM settings) could easily handle which
domain is in control, but that still does not mean that PF reps must be
created automatically, does it?

> That makes the thing looks more like a switch with cables being plugged
> in and out.

Yes, that's exactly how I view it as well.