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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,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 6065BC63798 for ; Tue, 24 Nov 2020 09:57:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 07F1B2076B for ; Tue, 24 Nov 2020 09:57:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cy8do4TV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731321AbgKXJ5W (ORCPT ); Tue, 24 Nov 2020 04:57:22 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:23845 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731568AbgKXJ5V (ORCPT ); Tue, 24 Nov 2020 04:57:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606211840; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mi0S82r7bzQoS3BczSKSMu4awfdr5Uu/IpAabFMazi4=; b=cy8do4TVFf/kErIV3/ii+KzPWg0eLkVIa8rz9XnxNLZnCrj4Stj+d8TsYTNOAbTEcAZTu0 AOcX0DmY6IVGYIhMvyyU4vQMJOBjHyGr116xfIGnVmWtjOqxvelXbAKPfNZ/9Pt9t0U6Dz rd0B3Z/baiJc/1TfiwOl8eYGjYt/ap8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-75-De7nGcK5NmeVNUhrXovq8Q-1; Tue, 24 Nov 2020 04:57:16 -0500 X-MC-Unique: De7nGcK5NmeVNUhrXovq8Q-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id F249A107AFAF; Tue, 24 Nov 2020 09:57:14 +0000 (UTC) Received: from gondolin (ovpn-113-136.ams2.redhat.com [10.36.113.136]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9BEEC60C13; Tue, 24 Nov 2020 09:57:10 +0000 (UTC) Date: Tue, 24 Nov 2020 10:57:07 +0100 From: Cornelia Huck To: Eric Farman Cc: Kirti Wankhede , Alex Williamson , Halil Pasic , Matthew Rosato , linux-s390@vger.kernel.org, kvm@vger.kernel.org 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> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: 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