netdev - Re: [PATCH net-next] net/mlx4_core: Fix backward compatibility on VFs

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Message-ID: <CAJ3xEMiKKULxXOrp6QmSCoD1SdXXYk6KLcnn2HdrcucmogpDGg@mail.gmail.com>
Date:	Sun, 20 Mar 2016 09:21:51 +0200
From:	Or Gerlitz <gerlitz.or@...il.com>
To:	Yuval Shaia <yuval.shaia@...cle.com>
Cc:	Eli Cohen <eli@...lanox.com>, David Miller <davem@...emloft.net>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Alexey Kardashevskiy <aik@...abs.ru>
Subject: Re: [PATCH net-next] net/mlx4_core: Fix backward compatibility on VFs

On Sun, Mar 20, 2016 at 9:07 AM, Yuval Shaia <yuval.shaia@...cle.com> wrote:
> On Fri, Mar 18, 2016 at 11:11:06PM -0400, David Miller wrote:
>> From: Eli Cohen <eli@...lanox.com>
>> Date: Thu, 17 Mar 2016 18:49:42 +0200

>> > Commit 85743f1eb345 ("net/mlx4_core: Set UAR page size to 4KB regardless
>> > of system page size") introduced dependency where old VF drivers without
>> > this fix fail to load if the PF driver runs with this commit.
>> > To resolve this add a module parameter which disables that functionality
>> > by default.  If both the PF and VFs are running with a driver with that
>> > commit the administrator may set the module param to true.
>> > The module parameter is called enable_4k_uar.

> Can you consider passing this via comm-channel and save us all from new
> module parameter?
> Suggesting this from sys-admin perspective where (1) making this consist in
> VF and **all** guests would me a nightmare and also (2) take into account
> in public cloud that hypervisor sys-admin is not necessary the same person
> as guest sys-admin.

AFAIK both modified (e.g containing the offending commit) and
non-modified VF drivers
need not be aware to the fix. It should be  a PF only param, where all types of
VF driver keeps working with their source of info being the comm-channel only.

Eli, Yishai, can you confirm this is the case?

Or.