Message-ID: <da7a2f2d-3ff5-0cd1-f166-79d7355f3df0@mellanox.com>
Date:   Wed, 5 Aug 2020 11:20:59 +0300
From:   Moshe Shemesh <moshe@...lanox.com>
To:     Vasundhara Volam <vasundhara-v.volam@...adcom.com>
Cc:     Jacob Keller <jacob.e.keller@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>,
        Netdev <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next RFC 00/13] Add devlink reload level option


On 8/5/2020 9:55 AM, Vasundhara Volam wrote:
> On Wed, Aug 5, 2020 at 12:02 PM Moshe Shemesh <moshe@...lanox.com> wrote:
>>
>> On 8/4/2020 1:13 PM, Vasundhara Volam wrote:
>>> On Mon, Aug 3, 2020 at 7:23 PM Moshe Shemesh <moshe@...lanox.com> wrote:
>>>> On 8/3/2020 3:47 PM, Vasundhara Volam wrote:
>>>>> On Mon, Aug 3, 2020 at 5:47 PM Moshe Shemesh <moshe@...lanox.com> wrote:
>>>>>> On 8/3/2020 1:24 PM, Vasundhara Volam wrote:
>>>>>>> On Tue, Jul 28, 2020 at 10:13 PM Jacob Keller <jacob.e.keller@...el.com> wrote:
>>>>>>>> On 7/27/2020 10:25 PM, Vasundhara Volam wrote:
>>>>>>>>> On Mon, Jul 27, 2020 at 4:36 PM Moshe Shemesh <moshe@...lanox.com> wrote:
>>>>>>>>>> Introduce new option on devlink reload API to enable the user to select the
>>>>>>>>>> reload level required. Complete support for all levels in mlx5.
>>>>>>>>>> The following reload levels are supported:
>>>>>>>>>>       driver: Driver entities re-instantiation only.
>>>>>>>>>>       fw_reset: Firmware reset and driver entities re-instantiation.
>>>>>>>>> The Name is a little confusing. I think it should be renamed to
>>>>>>>>> fw_live_reset (in which both firmware and driver entities are
>>>>>>>>> re-instantiated).  For only fw_reset, the driver should not undergo
>>>>>>>>> reset (it requires a driver reload for firmware to undergo reset).
>>>>>>>>>
>>>>>>>> So, I think the differentiation here is that "live_patch" doesn't reset
>>>>>>>> anything.
>>>>>>> This seems similar to flashing the firmware and does not reset anything.
>>>>>> The live patch is activating fw change without reset.
>>>>>>
>>>>>> It is not suitable for any fw change but fw gaps which don't require reset.
>>>>>>
>>>>>> I can query the fw to check if the pending image change is suitable or
>>>>>> require fw reset.
>>>>> Okay.
>>>>>>>>>>       fw_live_patch: Firmware live patching only.
>>>>>>>>> This level is not clear. Is this similar to flashing??
>>>>>>>>>
>>>>>>>>> Also I have a basic query. The reload command is split into
>>>>>>>>> reload_up/reload_down handlers (Please correct me if this behaviour is
>>>>>>>>> changed with this patchset). What if the vendor specific driver does
>>>>>>>>> not support up/down and needs only a single handler to fire a firmware
>>>>>>>>> reset or firmware live reset command?
>>>>>>>> In the "reload_down" handler, they would trigger the appropriate reset,
>>>>>>>> and quiesce anything that needs to be done. Then on reload up, it would
>>>>>>>> restore and bring up anything quiesced in the first stage.
>>>>>>> Yes, I got the "reload_down" and "reload_up". Similar to the device
>>>>>>> "remove" and "re-probe" respectively.
>>>>>>>
>>>>>>> But our requirement is a similar "ethtool reset" command, where
>>>>>>> ethtool calls a single callback in driver and driver just sends a
>>>>>>> firmware command for doing the reset. Once firmware receives the
>>>>>>> command, it will initiate the reset of driver and firmware entities
>>>>>>> asynchronously.
>>>>>> It is similar to mlx5 case here for fw_reset. The driver triggers the fw
>>>>>> command to reset and all PFs drivers gets events to handle and do
>>>>>> re-initialization.  To fit it to the devlink reload_down and reload_up,
>>>>>> I wait for the event handler to complete and it stops at driver unload
>>>>>> to have the driver up by devlink reload_up. See patch 8 in this patchset.
>>>>>>
>>>>> Yes, I see reload_down is triggering the reset. In our driver, after
>>>>> triggering the reset through a firmware command, reset is done in
>>>>> another context as the driver initiates the reset only after receiving
>>>>> an ASYNC event from the firmware.
>>>> Same here.
>>>>
>>>>> Probably, we have to use reload_down() to send firmware command to
>>>>> trigger reset and do nothing in reload_up.
>>>> I had that in previous version, but its wrong to use devlink reload this
>>>> way, so I added wait with timeout for the event handling to complete
>>>> before unload_down function ends. See mlx5_fw_wait_fw_reset_done(). Also
>>>> the event handler stops before load back to have that done by devlink
>>>> reload_up.
>>> But "devlink dev reload" will be invoked by the user only on a single
>>> dev handler and all function drivers will be re-instantiated upon the
>>> ASYNC event. reload_down and reload_up are invoked only the function
>>> which the user invoked.
>>>
>>> Take an example of a 2-port (PF0 and PF1) adapter on a single host and
>>> with some VFs loaded on the device. User invokes "devlink dev reload"
>>> on PF0, ASYNC event is received on 2 PFs and VFs for reset. All the
>>> function drivers will be re-instantiated including PF0.
>>>
>>> If we wait for some time in reload_down() of PF0 and then call load in
>>> reload_up(), this code will be different from other function drivers.
>>
>> I see your point here, but the user run devlink reload command on one
>> PF, in this case of fw-reset it will influence other PFs, but that's a
>> result of the fw-reset, the user if asked for params change or namespace
>> change that was for this PF.
> Right, if any driver is implementing only fw-reset have to leave
> reload_up as an empty function.


No, its not only up the driver. The netns option is implemented by 
devlink and its running between reload_down and reload_up.

>>>>>     And returning from reload
>>>>> does not mean that reset is complete as it is done in another context
>>>>> and the driver notifies the health reporter once the reset is
>>>>> complete. devlink framework may have to allow drivers to implement
>>>>> reload_down only to look more clean or call reload_up only if the
>>>>> driver notifies the devlink once reset is completed from another
>>>>> context. Please suggest.

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