From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:55483 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731321AbgKXJ5V (ORCPT ); Tue, 24 Nov 2020 04:57:21 -0500 Date: Tue, 24 Nov 2020 10:57:07 +0100 From: Cornelia Huck Subject: Re: [PATCH v2 1/2] vfio-mdev: Wire in a request handler for mdev parent Message-ID: <20201124105707.7f5802eb.cohuck@redhat.com> In-Reply-To: <20201120180740.87837-2-farman@linux.ibm.com> References: <20201120180740.87837-1-farman@linux.ibm.com> <20201120180740.87837-2-farman@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-ID: To: Eric Farman Cc: Kirti Wankhede , Alex Williamson , Halil Pasic , Matthew Rosato , linux-s390@vger.kernel.org, kvm@vger.kernel.org On Fri, 20 Nov 2020 19:07:39 +0100 Eric Farman wrote: > While performing some destructive tests with vfio-ccw, where the > paths to a device are forcible removed and thus the device itself > is unreachable, it is rather easy to end up in an endless loop in > vfio_del_group_dev() due to the lack of a request callback for the > associated device. > > In this example, one MDEV (77c) is used by a guest, while another > (77b) is not. The symptom is that the iommu is detached from the > mdev for 77b, but not 77c, until that guest is shutdown: > > [ 238.794867] vfio_ccw 0.0.077b: MDEV: Unregistering > [ 238.794996] vfio_mdev 11f2d2bc-4083-431d-a023-eff72715c4f0: Removing from iommu group 2 > [ 238.795001] vfio_mdev 11f2d2bc-4083-431d-a023-eff72715c4f0: MDEV: detaching iommu > [ 238.795036] vfio_ccw 0.0.077c: MDEV: Unregistering > ...silence... > > Let's wire in the request call back to the mdev device, so that a > device being physically removed from the host can be (gracefully?) > handled by the parent device at the time the device is removed. > > Add a message when registering the device if a driver doesn't > provide this callback, so a clue is given that this same loop > may be encountered in a similar situation. > > Signed-off-by: Eric Farman > --- > drivers/vfio/mdev/mdev_core.c | 4 ++++ > drivers/vfio/mdev/vfio_mdev.c | 10 ++++++++++ > include/linux/mdev.h | 4 ++++ > 3 files changed, 18 insertions(+) Reviewed-by: Cornelia Huck