netdev - Re: [PATCH V2 net 00/11] Extending the ena driver to support new features and enhance performance

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Date:   Thu, 6 Jun 2019 16:42:19 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     "Bshara, Nafea" <nafea@...zon.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Jubran, Samih" <sameehj@...zon.com>, Andrew Lunn <andrew@...n.ch>,
        "Kiyanovski, Arthur" <akiyano@...zon.com>,
        "Bshara, Saeed" <saeedb@...zon.com>,
        "Tzalik, Guy" <gtzalik@...zon.com>,
        "Matushevsky, Alexander" <matua@...zon.com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        "Saidi, Ali" <alisaidi@...zon.com>,
        "Machulsky, Zorik" <zorik@...zon.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Wilson, Matt" <msw@...zon.com>,
        "Belgazal, Netanel" <netanel@...zon.com>,
        "Herrenschmidt, Benjamin" <benh@...zon.com>,
        Jiri Pirko <jiri@...nulli.us>
Subject: Re: [PATCH V2 net 00/11] Extending the ena driver to support new
 features and enhance performance

On Thu, 6 Jun 2019 23:21:25 +0000, Bshara, Nafea wrote:
> > On Jun 6, 2019, at 4:08 PM, Jakub Kicinski <jakub.kicinski@...ronome.com> wrote:
> > On Thu, 6 Jun 2019 22:57:21 +0000, Bshara, Nafea wrote:  
> >>> Having said that, it's entirely unclear to me what the user scenario is
> >>> here.  You say "which two devices related", yet you only have one bit,
> >>> so it can indicate that there is another device, not _which_ device is
> >>> related.  Information you can full well get from running lspci 🤷
> >>> Do the devices have the same PCI ID/vendor:model?    
> >> 
> >> Different model id  
> > 
> > Okay, then you know which one is which.  Are there multiple ENAs but
> > one EFA?
> 
> Yes,  very possible. Very common
> 
> Typical use case that instances have one ena for control plane, one
> for internet facing , and one 100G ena that also have efa capabilities

I see, and those are PCI devices..  Some form of platform data would
seem like the best fit to me.  There is something called:

/sys/bus/pci/${dbdf}/label

It seems to come from some ACPI table - DSM maybe?  I think you can put
whatever string you want there 🤔

> >> Will look into sysfs   
> > 
> > I still don't understand what is the problem you're trying to solve,
> > perhaps phys_port_id is the way to go...
> > 
> > 
> > The larger point here is that we can't guide you to the right API
> > unless we know what you're trying to achieve.  And we don't have 
> > the slightest clue of what're trying to achieve if uAPI is forwarded 
> > to the device.  
> > 
> > Honestly this is worse, and way more basic than I thought, I think
> > 315c28d2b714 ("net: ena: ethtool: add extra properties retrieval via get_priv_flags")
> > needs to be reverted.  
> 
> Let’s not do that until we finish this discussion and explain the various use cases

Whatever we decide is the right API for tagging interfaces in a virtual
environment, it's definitely not going to be private feature flags.