netdev - Re: [net-next v2 1/1] virtual-bus: Implementation of Virtual Bus

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Date:   Wed, 20 Nov 2019 17:05:00 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Jason Wang <jasowang@...hat.com>,
        Parav Pandit <parav@...lanox.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Dave Ertman <david.m.ertman@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "sassmann@...hat.com" <sassmann@...hat.com>,
        Kiran Patil <kiran.patil@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Bie, Tiwei" <tiwei.bie@...el.com>
Subject: Re: [net-next v2 1/1] virtual-bus: Implementation of Virtual Bus

On Wed, Nov 20, 2019 at 12:45:25PM -0400, Jason Gunthorpe wrote:
> > > For instance, this VFIO based approach might be very suitable to the
> > > intel VF based ICF driver, but we don't yet have an example of non-VF
> > > HW that might not be well suited to VFIO.
> >
> > I don't think we should keep moving the goalposts like this.
> 
> It is ABI, it should be done as best we can as we have to live with it
> for a long time. Right now HW is just starting to come to market with
> VDPA and it feels rushed to design a whole subsystem style ABI around
> one, quite simplistic, driver example.

Well one has to enable hardware in some way. It's not really reasonable
to ask for multiple devices to be available just so there's a driver and
people can use them. At this rate no one will want to be the first to
ship new devices ;)

> > If people write drivers and find some infrastruture useful,
> > and it looks more or less generic on the outset, then I don't
> > see why it's a bad idea to merge it.
> 
> Because it is userspace ABI, caution is always justified when defining
> new ABI.


Reasonable caution, sure. Asking Alex to block Intel's driver until
someone else catches up and ships competing hardware isn't reasonable
though. If that's your proposal I guess we'll have to agree to disagree.

-- 
MST