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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 40320C433ED for ; Fri, 23 Apr 2021 11:44:35 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7111A61409 for ; Fri, 23 Apr 2021 11:44:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7111A61409 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51416 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lZuEb-0004cX-C8 for qemu-devel@archiver.kernel.org; Fri, 23 Apr 2021 07:44:33 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41264) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZuDG-00048k-J2 for qemu-devel@nongnu.org; Fri, 23 Apr 2021 07:43:10 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:48969) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZuDA-0004R9-Ap for qemu-devel@nongnu.org; Fri, 23 Apr 2021 07:43:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619178183; 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=Y+0OyCaxFL2j0gb0EGrpX16/O5YlTCPU5PWIfR0m3yI=; b=PFB3OMBr1WlTEME3+nn6tOcmloJAnmvF5KJDnIlb5xVTo5J4DYfV7iMLqjGjmdQrW6fsdz TmXj2kNHSFuXy4+GVF5/JZLKqRdE2MFr9EGvn21/boPKe3dk2APe9uXd/r6h/B21seHsZ7 LznpZ4BNe2gceG8PoBGKbRulP0RQxn8= 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-565-B_aj2zSiNTqtOQDd7efv5g-1; Fri, 23 Apr 2021 07:43:00 -0400 X-MC-Unique: B_aj2zSiNTqtOQDd7efv5g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7C6FA18397A5; Fri, 23 Apr 2021 11:42:59 +0000 (UTC) Received: from gondolin.fritz.box (ovpn-113-167.ams2.redhat.com [10.36.113.167]) by smtp.corp.redhat.com (Postfix) with ESMTP id 03F3C10023AC; Fri, 23 Apr 2021 11:42:54 +0000 (UTC) Date: Fri, 23 Apr 2021 13:42:52 +0200 From: Cornelia Huck To: Eric Farman Subject: Re: [PATCH v2] vfio-ccw: Permit missing IRQs Message-ID: <20210423134252.264059e5.cohuck@redhat.com> In-Reply-To: <20210421152053.2379873-1-farman@linux.ibm.com> References: <20210421152053.2379873-1-farman@linux.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=cohuck@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-s390x@nongnu.org, Alex Williamson , qemu-devel@nongnu.org, Matthew Rosato Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, 21 Apr 2021 17:20:53 +0200 Eric Farman wrote: > Commit 690e29b91102 ("vfio-ccw: Refactor ccw irq handler") changed > one of the checks for the IRQ notifier registration from saying > "the host needs to recognize the only IRQ that exists" to saying > "the host needs to recognize ANY IRQ that exists." > > And this worked fine, because the subsequent change to support the > CRW IRQ notifier doesn't get into this code when running on an older > kernel, thanks to a guard by a capability region. The later addition > of the REQ(uest) IRQ by commit b2f96f9e4f5f ("vfio-ccw: Connect the > device request notifier") broke this assumption because there is no > matching capability region. Thus, running new QEMU on an older > kernel fails with: > > vfio: unexpected number of irqs 2 > > Let's adapt the message here so that there's a better clue of what > IRQ is missing. > > Furthermore, let's make the REQ(uest) IRQ not fail when attempting > to register it, to permit running vfio-ccw on a newer QEMU with an > older kernel. > > Fixes: b2f96f9e4f5f ("vfio-ccw: Connect the device request notifier") > Signed-off-by: Eric Farman > --- > > Notes: > v1->v2: > - Keep existing "invalid number of IRQs" message with adapted text [CH] > - Move the "is this an error" test to the registration of the IRQ in > question, rather than making it allowable for any IRQ mismatch [CH] > - Drop Fixes tag for initial commit [EF] > > v1: https://lore.kernel.org/qemu-devel/20210419184906.2847283-1-farman@linux.ibm.com/ > > hw/vfio/ccw.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c > index b2df708e4b..400bc07fe2 100644 > --- a/hw/vfio/ccw.c > +++ b/hw/vfio/ccw.c > @@ -412,8 +412,8 @@ static void vfio_ccw_register_irq_notifier(VFIOCCWDevice *vcdev, > } > > if (vdev->num_irqs < irq + 1) { > - error_setg(errp, "vfio: unexpected number of irqs %u", > - vdev->num_irqs); > + error_setg(errp, "vfio: IRQ %u not available (number of irqs %u)", > + irq, vdev->num_irqs); > return; > } > > @@ -696,13 +696,15 @@ static void vfio_ccw_realize(DeviceState *dev, Error **errp) > > vfio_ccw_register_irq_notifier(vcdev, VFIO_CCW_REQ_IRQ_INDEX, &err); > if (err) { > - goto out_req_notifier_err; > + /* > + * Report this error, but do not make it a failing condition. > + * Lack of this IRQ in the host does not prevent normal operation. > + */ > + error_report_err(err); > } > > return; > > -out_req_notifier_err: > - vfio_ccw_unregister_irq_notifier(vcdev, VFIO_CCW_CRW_IRQ_INDEX); > out_crw_notifier_err: > vfio_ccw_unregister_irq_notifier(vcdev, VFIO_CCW_IO_IRQ_INDEX); > out_io_notifier_err: Patch looks good to me, but now I'm wondering: Is calling vfio_ccw_unregister_irq_notifier() for an unregistered irq actually safe? I think it is (our notifiers are always present, and we should handle any ioctl failure gracefully), but worth a second look. In fact, we already unregister the crw irq unconditionally, so we would likely already have seen any problems for that one, so I assume all is good.