netdev - Re: [pull request][net-next V10 00/14] Add mlx5 subfunction support

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Date:   Sun, 24 Jan 2021 12:47:07 -0800
From:   Edwin Peer <edwin.peer@...adcom.com>
To:     Saeed Mahameed <saeed@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        netdev <netdev@...r.kernel.org>, linux-rdma@...r.kernel.org,
        Alexander Duyck <alexander.duyck@...il.com>,
        Sridhar Samudrala <sridhar.samudrala@...el.com>,
        David Ahern <dsahern@...nel.org>,
        Kiran Patil <kiran.patil@...el.com>,
        Jacob Keller <jacob.e.keller@...el.com>,
        "Ertman, David M" <david.m.ertman@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Saeed Mahameed <saeedm@...dia.com>
Subject: Re: [pull request][net-next V10 00/14] Add mlx5 subfunction support

On Fri, Jan 22, 2021 at 11:37 AM Saeed Mahameed <saeed@...nel.org> wrote:

> This series form Parav was the theme of this mlx5 release cycle,
> we've been waiting anxiously for the auxbus infrastructure to make it into
> the kernel, and now as the auxbus is in and all the stars are aligned, I
> can finally submit this patchset of the devlink and mlx5 subfunction support.
>
> For more detailed information about subfunctions please see detailed tag
> log below.

Apologies for the tardy question out of left field, but I've been
thinking about this some more. If I recall, the primary motivation for
this was a means to effectively address more VFs? But, why can't the
device simply expose more bus numbers?

>From the PCI spec:

"SR-IOV Devices may consume more than one Bus Number. A VF can be
associated with any Bus Number within
the Device’s Bus Number range - the captured Bus Number plus any
additional Bus Numbers configured by
software. See Section 9.2.1.2 for details.

- Use of multiple Bus Numbers enables a device to support a very large
number of VFs - up to the size
of the Routing ID space minus the bits used to identify intervening busses"

Regards,
Edwin Peer

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