From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:30544 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725793AbgLUPsK (ORCPT ); Mon, 21 Dec 2020 10:48:10 -0500 Date: Mon, 21 Dec 2020 16:46:34 +0100 From: Cornelia Huck Subject: Re: [RFC 1/1] s390/cio: Remove uevent-suppress from css driver Message-ID: <20201221164634.11cd3813.cohuck@redhat.com> In-Reply-To: <20201219073316.1be609d5.pasic@linux.ibm.com> References: <20201124093407.23189-1-vneethv@linux.ibm.com> <20201124093407.23189-2-vneethv@linux.ibm.com> <20201124140220.77c65539.cohuck@redhat.com> <4be7e163-1118-d365-7d25-df39ba78181f@linux.vnet.ibm.com> <0b4e34b7-7a4e-71b0-8a64-ea909e64f416@linux.ibm.com> <20201208183054.44f4fc2d.cohuck@redhat.com> <20201209135203.0008ab18.pasic@linux.ibm.com> <20201215191307.281c6e6f.cohuck@redhat.com> <20201219073316.1be609d5.pasic@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-ID: To: Halil Pasic Cc: Vineeth Vijayan , Vineeth Vijayan , oberpar@linux.ibm.com, linux-s390@vger.kernel.org, farman@linux.ibm.com, fiuczy@linux.ibm.com On Sat, 19 Dec 2020 07:33:16 +0100 Halil Pasic 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! 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.