From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB397C43381 for ; Thu, 14 Feb 2019 15:40:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8FF33222A1 for ; Thu, 14 Feb 2019 15:40:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2502209AbfBNPkw (ORCPT ); Thu, 14 Feb 2019 10:40:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:21885 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2502131AbfBNPkt (ORCPT ); Thu, 14 Feb 2019 10:40:49 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 36370C070473; Thu, 14 Feb 2019 15:40:49 +0000 (UTC) Received: from gondolin (dhcp-192-213.str.redhat.com [10.33.192.213]) by smtp.corp.redhat.com (Postfix) with ESMTP id B29AD1A912; Thu, 14 Feb 2019 15:40:46 +0000 (UTC) Date: Thu, 14 Feb 2019 16:40:44 +0100 From: Cornelia Huck To: Christian Borntraeger Cc: Pierre Morel , alex.williamson@redhat.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, frankja@linux.ibm.com, akrowiak@linux.ibm.com, pasic@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com, mimu@linux.ibm.com Subject: Re: [PATCH v3 1/9] s390: vfio_ap: link the vfio_ap devices to the vfio_ap bus subsystem Message-ID: <20190214164044.5e67660a.cohuck@redhat.com> In-Reply-To: <6147f1ce-fd8b-1ec2-30ce-7ac68f3d8e27@de.ibm.com> References: <1550152269-6317-1-git-send-email-pmorel@linux.ibm.com> <1550152269-6317-2-git-send-email-pmorel@linux.ibm.com> <20190214155441.087d2a68.cohuck@redhat.com> <6147f1ce-fd8b-1ec2-30ce-7ac68f3d8e27@de.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 14 Feb 2019 15:40:49 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 14 Feb 2019 16:05:35 +0100 Christian Borntraeger wrote: > On 14.02.2019 15:54, Cornelia Huck wrote: > > On Thu, 14 Feb 2019 14:51:01 +0100 > > Pierre Morel wrote: > > Pierre, > this is independent from this series and should have been sent separately. > In the end (when we have the final solution) this will require cc stable. > > > >> Libudev relies on having a subsystem link for non-root devices. To > >> avoid libudev (and potentially other userspace tools) choking on the > >> matrix device let us introduce a vfio_ap bus and with that the vfio_ap > >> bus subsytem, and make the matrix device reside within it. > > > > How does libudev choke on this? It feels wrong to introduce a bus that > > basically does nothing... > > I have seen libvirt looping when a matrix device was available before the > libvirt start. > Marc Hartmayer debugged this and circumvented this in libvirt: > https://www.redhat.com/archives/libvir-list/2019-February/msg00837.html > > Still libudev expects a subsystem link in the matrix folder when doing the > udev_enumerate_scan_devices call. > > Having a bus is one way of adding a subsystem link. Ugh, that feels really broken. Adding a bus is probably the easiest way to get this working, though :/