Re: [PATCH net-next RFC 01/13] devlink: Add reload level option to devlink reload command

From: Jakub Kicinski
Date: Tue Jul 28 2020 - 14:45:06 EST

On Tue, 28 Jul 2020 09:47:00 -0700 Jacob Keller wrote:
> On 7/28/2020 6:58 AM, Jiri Pirko wrote:
> > But this is needed to maintain the existing behaviour which is different
> > for different drivers.
> Which drivers behave differently here?

I think Jiri refers to mlxsw vs mlx5.

mlxsw loads firmware on probe, by default at least. So reloading the
driver implies a FW reset. NIC drivers OTOH don't generally load FW
so they didn't reset FW.

Now since we're redefining the API from "do a reload so that driverinit
params are applied" (or "so that all netdevs get spawned in a new
netns") to "do a reset of depth X" we have to change the paradigm.

What I was trying to suggest is that we should not have to re-define
the API like this.

From user perspective what's important is what the reset achieves (and
perhaps how destructive it is). We can define the reset levels as:

$ devlink dev reload pci/0000:82:00.0 net-ns-respawn
$ devlink dev reload pci/0000:82:00.0 driver-param-init
$ devlink dev reload pci/0000:82:00.0 fw-activate

combining should be possible when user wants multiple things to happen:

$ devlink dev reload pci/0000:82:00.0 fw-activate driver-param-init

Then we have the use case of a "live reset" which is slightly
under-defined right now IMHO, but we can extend it as:

$ devlink dev reload pci/0000:82:00.0 fw-activate --live

We can also add the "reset level" specifier - for the cases where
device is misbehaving:

$ devlink dev reload pci/0000:82:00.0 level [driver|fw|hardware]

But I don't think that we can go from the current reload command
cleanly to just a level reset. The driver-specific default is a bad
smell which indicates we're changing semantics from what user wants
to what the reset depth is. Our semantics with the patch as it stands
are in fact:
- if you want to load new params or change netns, don't pass the level
- the "driver default" workaround dictates the right reset level for
param init;
- if you want to activate new firmware - select the reset level you'd
like from the reset level options.