Re: [RFC 1/1] s390/cio: Remove uevent-suppress from css driver

[Boris Fiuczynski <fiuczy@linux.ibm.com>]

On 12/21/20 5:51 PM, Halil Pasic wrote:
> On Mon, 21 Dec 2020 16:46:34 +0100
> Cornelia Huck <cohuck@redhat.com> wrote:
> 
>> On Sat, 19 Dec 2020 07:33:16 +0100
>> Halil Pasic <pasic@linux.ibm.com> wrote:
>>
>>> I finally came around to test this. In my experience driverctl works for
>>> subchannels and vfio_ccw without this patch, and continues to work with
>>> it. I found the code in driverctl that does the unbind and the implicit
>>> bind (via drivers_probe after after driver_override was set).
>>>
>>> So now I have to ask, how exactly was the original problem diagnosed?
>>>
>>> In https://marc.info/?l=linux-s390&m=158591045732735&w=2 there is a
>>> paragraph like:
>>>
>>> """
>>> So while there's definitely a good reason for wanting to delay uevents,
>>> it is also introducing problems. One is udev rules for subchannels that
>>> are supposed to do something before a driver binds (e.g. setting
>>> driver_override to bind an I/O subchannel to vfio_ccw instead of
>>> io_subchannel) are not effective, as the ADD uevent will only be
>>> generated when the io_subchannel driver is already done with doing all
>>> setup. Another one is that only the ADD uevent is generated after
>>> uevent suppression is lifted; any other uevents that might have been
>>> generated are lost.
>>> """
>>>
>>> This is not how driverclt works! I.e. it deals with the situation that
>>> the I/O subchannel was already bound to the io_subchannel driver at
>>> the time the udev rule installed by driverctl activates (via the
>>> mechanism I described above).
>>
>> That's... weird. It definitely did not work on the LPAR I initially
>> tried it out on!
>>
> 
> I think Boris told me some weeks ago that it didn't work for him either.
> I will check with him after the winter sleep.

Yesterday I used driverctl successfully for a subchannel on F33.

Not sure what went wrong a couple of months ago but I cannot reproduce 
driverctl not working now.

> 
>> However, I think removing the suppression still looks like a good idea:
>> we still have the "any uevent other than ADD will have been lost"
>> problem.
>>
I totally agree with this.

> 
> I agree. I didn't look into the details, in general I think removing
> quirks specific to 390 (when possible) is a good thing.
> 
> Regards,
> Halil
> 


-- 
Mit freundlichen Grüßen/Kind regards
    Boris Fiuczynski

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