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=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 56DCCC388F2 for ; Mon, 2 Nov 2020 14:36:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA14E20731 for ; Mon, 2 Nov 2020 14:36:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="fA5wTIdH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725926AbgKBOgA (ORCPT ); Mon, 2 Nov 2020 09:36:00 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:31236 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725788AbgKBOgA (ORCPT ); Mon, 2 Nov 2020 09:36:00 -0500 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0A2EWn0v048477; Mon, 2 Nov 2020 09:35:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=b7I5sNXEMJ08KuQzqBBjubSlvLzoNo1iWKblvYCHXlE=; b=fA5wTIdH/DpCUT6/jNdfS1Yq9MbuWASpftXoqnx76IdB0VS4QYXO0BTiDsWbZiM20bia nxVM1RB9e8Cx6IfzETE17L45ZPdGX5Gi0VOLfI5fTlHKrQ7HKpDG7YcPs0tet21vWEI8 NMdPab5/zubqCxZetAClf4SN2GXiGVK+e+KX0CfOS3bBosEENcz7IcTgRop07i2U6gHa r0L06OpEy21WyhSbbISXUpCiORkS9nBQ4svZAzcUhWft3l4Khlax1B2wtJ38rlrhlxvS zTiMOLtczoiG3O4pI60NeJf1zWl/qy2KFRUMfKe4rD+X0WBoNTPwBOySrIsMEMF2bDAZ Yw== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 34jfjpgwpq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 02 Nov 2020 09:35:52 -0500 Received: from m0098416.ppops.net (m0098416.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 0A2EXI2K052483; Mon, 2 Nov 2020 09:35:52 -0500 Received: from ppma03dal.us.ibm.com (b.bd.3ea9.ip4.static.sl-reverse.com [169.62.189.11]) by mx0b-001b2d01.pphosted.com with ESMTP id 34jfjpgwp6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 02 Nov 2020 09:35:52 -0500 Received: from pps.filterd (ppma03dal.us.ibm.com [127.0.0.1]) by ppma03dal.us.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 0A2EX3sg006891; Mon, 2 Nov 2020 14:35:51 GMT Received: from b01cxnp22036.gho.pok.ibm.com (b01cxnp22036.gho.pok.ibm.com [9.57.198.26]) by ppma03dal.us.ibm.com with ESMTP id 34hs32e1ch-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 02 Nov 2020 14:35:51 +0000 Received: from b01ledav005.gho.pok.ibm.com (b01ledav005.gho.pok.ibm.com [9.57.199.110]) by b01cxnp22036.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0A2EZnB521627846 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 2 Nov 2020 14:35:49 GMT Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A8FF9AE05C; Mon, 2 Nov 2020 14:35:49 +0000 (GMT) Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E9766AE063; Mon, 2 Nov 2020 14:35:48 +0000 (GMT) Received: from cpe-66-24-58-13.stny.res.rr.com (unknown [9.85.162.174]) by b01ledav005.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 2 Nov 2020 14:35:48 +0000 (GMT) Subject: Re: [PATCH v11 01/14] s390/vfio-ap: No need to disable IRQ after queue reset To: Halil Pasic Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@linux.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.com, mjrosato@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com, fiuczy@linux.ibm.com, frankja@linux.ibm.com, david@redhat.com, hca@linux.ibm.com, gor@linux.ibm.com References: <20201022171209.19494-1-akrowiak@linux.ibm.com> <20201022171209.19494-2-akrowiak@linux.ibm.com> <20201027074846.30ee0ddc.pasic@linux.ibm.com> <7a2c5930-9c37-8763-7e5d-c08a3638e6a1@linux.ibm.com> <20201030184242.3bceee09.pasic@linux.ibm.com> <20201031044329.77b5a249.pasic@linux.ibm.com> From: Tony Krowiak Message-ID: <76140b31-a747-0f4e-438f-835ba13752d5@linux.ibm.com> Date: Mon, 2 Nov 2020 09:35:48 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20201031044329.77b5a249.pasic@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-02_07:2020-11-02,2020-11-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 spamscore=0 phishscore=0 adultscore=0 suspectscore=11 impostorscore=0 bulkscore=0 malwarescore=0 mlxscore=0 mlxlogscore=989 lowpriorityscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011020112 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 10/30/20 11:43 PM, Halil Pasic wrote: > On Fri, 30 Oct 2020 16:37:04 -0400 > Tony Krowiak wrote: > >> On 10/30/20 1:42 PM, Halil Pasic wrote: >>> On Thu, 29 Oct 2020 19:29:35 -0400 >>> Tony Krowiak wrote: >>> >>>>>> @@ -1177,7 +1166,10 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev) >>>>>> */ >>>>>> if (ret) >>>>>> rc = ret; >>>>>> - vfio_ap_irq_disable_apqn(AP_MKQID(apid, apqi)); >>>>>> + q = vfio_ap_get_queue(matrix_mdev, >>>>>> + AP_MKQID(apid, apqi)); >>>>>> + if (q) >>>>>> + vfio_ap_free_aqic_resources(q); >>>>> Is it safe to do vfio_ap_free_aqic_resources() at this point? I don't >>>>> think so. I mean does the current code (and vfio_ap_mdev_reset_queue() >>>>> in particular guarantee that the reset is actually done when we arrive >>>>> here)? BTW, I think we have a similar problem with the current code as >>>>> well. >>>> If the return code from the vfio_ap_mdev_reset_queue() function >>>> is zero, then yes, we are guaranteed the reset was done and the >>>> queue is empty. >>> I've read up on this and I disagree. We should discuss this offline. >> Maybe you are confusing things here; my statement is specific to the return >> code from the vfio_ap_mdev_reset_queue() function, not the response code >> from the PQAP(ZAPQ) instruction. The vfio_ap_mdev_reset_queue() >> function issues the PQAP(ZAPQ) instruction and if the status response code >> is 0 indicating the reset was successfully initiated, it waits for the >> queue to empty. When the queue is empty, it returns 0 to indicate >> the queue is reset. >> If the queue does not become empty after a period of >> time, >> it will issue a warning (WARN_ON_ONCE) and return 0. In that case, I suppose >> there is no guarantee the reset was done, so maybe a change needs to be >> made there such as a non-zero return code. >> > I've overlooked the wait for empty. Maybe that return 0 had a part in > it. I now remember me insisting on having the wait code added when the > interrupt support was in the make. Sorry! > > If we have given up on out of retries retries, we are in trouble anyway. > >>> >>>>   The function returns a non-zero return code if >>>> the reset fails or the queue the reset did not complete within a given >>>> amount of time, so maybe we shouldn't free AQIC resources when >>>> we get a non-zero return code from the reset function? >>>> >>> If the queue is gone, or broken, it won't produce interrupts or poke the >>> notifier bit, and we should clean up the AQIC resources. >> True, which is what the code provided by this patch does; however, >> the AQIC resources should be cleaned up only if the KVM pointer is >> not NULL for reasons discussed elsewhere. > Yes, but these should be cleaned up before the KVM pointer becomes > null. We don't want to keep the page with the notifier byte pinned > forever, or? No, we do not want to keep the page forever. I probably should have been clearer. There are times we do a reset - e.g., on remove of the mdev - at which time there should be no KVM pointer, or else the remove will not be allowed. Of course, we won't do the reset either, so I guess you can ignore my comment. If there is no KVM pointer yet a page remains pinned, something bad happened.