netdev - Re: [net-next 1/4] gve: Add basic driver framework for Compute Engine Virtual NIC

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Message-ID: <CAH_-1qxdG2nFXTQs30nVanmNuEmENV-bf=60NpAZPy9j3EjyWg@mail.gmail.com>
Date:   Fri, 28 Jun 2019 16:05:05 -0700
From:   Catherine Sullivan <csully@...gle.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        netdev@...r.kernel.org, Sagi Shahar <sagis@...gle.com>,
        Jon Olson <jonolson@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Luigi Rizzo <lrizzo@...gle.com>
Subject: Re: [net-next 1/4] gve: Add basic driver framework for Compute Engine
 Virtual NIC

On Fri, Jun 28, 2019 at 1:06 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> On Fri, Jun 28, 2019 at 11:46:15AM -0700, Jakub Kicinski wrote:
> > On Fri, 28 Jun 2019 10:52:27 -0700, Catherine Sullivan wrote:
> > > > > +if NET_VENDOR_GOOGLE
> > > > > +
> > > > > +config GVE
> > > > > +     tristate "Google Virtual NIC (gVNIC) support"
> > > > > +     depends on (PCI_MSI && X86)
> > > >
> > > > We usually prefer for drivers not to depend on the platform unless
> > > > really necessary, but IDK how that applies to the curious new world
> > > > of NICs nobody can buy :)
> > >
> > > This is the only platform it will ever need to run on so we would really
> > > prefer to not have to support others :)
> >
> > I think the motivation is partially to force the uniform use of generic
> > APIs across the drivers, so that re-factoring of core code is easier.
> > Do you have any specific pain-points in mind where x86 dependency
> > simplifies things? If not I think it's a better default to not have it.
> > Not a big deal, though.
>
> And maybe sometime in the future you might want to put this interface
> in an ARM64 server?
>
> One 'pain-paint' is that the driver might assume cache-coherency,
> which is an x86 thing. If the generic APIs have been used, it should
> not be an issue, but i've not spent the time to see if the DMA API has
> been used correctly.
>
>      Andrew

Mostly it is just hesitation around lack of testing. But I've done a few quick
compile tests and ARM and ARM64 don't seem to have any problems so
I've removed the dependency in v3.