netdev - Re: phys_port_id in switchdev mode?

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Message-ID: <20180828204351.34fe457f@cakuba.netronome.com>
Date:   Tue, 28 Aug 2018 20:43:51 +0200
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Or Gerlitz <gerlitz.or@...il.com>,
        Simon Horman <simon.horman@...ronome.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "mchan@...adcom.com" <mchan@...adcom.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Frederick Botha <frederick.botha@...ronome.com>
Cc:     nick viljoen <nick.viljoen@...ronome.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: phys_port_id in switchdev mode?

Ugh, CC: netdev..

On Tue, 28 Aug 2018 20:05:39 +0200, Jakub Kicinski wrote:
> Hi!
> 
> I wonder if we can use phys_port_id in switchdev to group together
> interfaces of a single PCI PF?  Here is the problem:
> 
> With a mix of PF and VF interfaces it gets increasingly difficult to
> figure out which one corresponds to which PF.  We can identify which
> *representor* is which, by means of phys_port_name and devlink
> flavours.  But if the actual VF/PF interfaces are also present on the
> same host, it gets confusing when one tries to identify the PF they
> came from.  Generally one has to resort of matching between PCI DBDF of
> the PF and VFs or read relevant info out of ethtool -i.
> 
> In multi host scenario this is particularly painful, as there seems to
> be no immediately obvious way to match PCI interface ID of a card (0,
> 1, 2, 3, 4...) to the DBDF we have connected.
> 
> Another angle to this is legacy SR-IOV NDOs.  User space picks a netdev
> from /sys/bus/pci/$VF_DBDF/physfn/net/ to run the NDOs on in somehow
> random manner, which means we have to provide those for all devices with
> link to the PF (all reprs).  And we have to link them (a) because it's
> right (tm) and (b) to get correct naming.  The only reliable way to make
> user space (libvirt) choose the repr it should run the NDOs on (which is
> IMHO the corresponding PF repr) is to set phys_port_id on actual VFs,
> VF reprs, PFs and PF reprs to a value corresponding to the *PCI PF*,
> not the external/Ethernet port when in switchdev mode.  User space
> should understand phys_port_id in this context, given it was originally
> introduced for matching VFs to ports.
> 
> I hope this explanation makes sense, and is correct.  Please point out
> errors in my understanding, any comments would be appreciated! :)
> 
> Jiri?  Or?  Others?