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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 5D9C7C43387 for ; Mon, 7 Jan 2019 17:38:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2FEED2087F for ; Mon, 7 Jan 2019 17:38:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727632AbfAGRiL (ORCPT ); Mon, 7 Jan 2019 12:38:11 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:58828 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726942AbfAGRiL (ORCPT ); Mon, 7 Jan 2019 12:38:11 -0500 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id x07HULek146078 for ; Mon, 7 Jan 2019 12:38:10 -0500 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0a-001b2d01.pphosted.com with ESMTP id 2pvb4c8r5p-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 07 Jan 2019 12:38:09 -0500 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 7 Jan 2019 17:38:05 -0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x07Hc3u749938528 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 7 Jan 2019 17:38:03 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 864CEAE04D; Mon, 7 Jan 2019 17:38:03 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 223CEAE05A; Mon, 7 Jan 2019 17:38:03 +0000 (GMT) Received: from [9.152.96.120] (unknown [9.152.96.120]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 7 Jan 2019 17:38:03 +0000 (GMT) Reply-To: mimu@linux.ibm.com Subject: Re: [PATCH v5 10/15] KVM: s390: add functions to (un)register GISC with GISA To: Cornelia Huck , Pierre Morel Cc: KVM Mailing List , Linux-S390 Mailing List , linux-kernel@vger.kernel.org, Martin Schwidefsky , Heiko Carstens , Christian Borntraeger , Janosch Frank , David Hildenbrand , Halil Pasic References: <20181219191756.57973-1-mimu@linux.ibm.com> <20181219191756.57973-11-mimu@linux.ibm.com> <20190104141836.0ca98a77.cohuck@redhat.com> From: Michael Mueller Organization: IBM Date: Mon, 7 Jan 2019 18:38:02 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: <20190104141836.0ca98a77.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19010717-0016-0000-0000-000002417F51 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19010717-0017-0000-0000-0000329B8EE7 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-01-07_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901070150 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04.01.19 14:19, Cornelia Huck wrote: > On Wed, 2 Jan 2019 18:29:00 +0100 > Pierre Morel wrote: > >> On 19/12/2018 20:17, Michael Mueller wrote: >>> Add the IAM (Interruption Alert Mask) to the architecture specific >>> kvm struct. This mask in the GISA is used to define for which ISC >>> a GIB alert can be issued. >>> >>> The functions kvm_s390_gisc_register() and kvm_s390_gisc_unregister() >>> are used to (un)register a GISC (guest ISC) with a virtual machine and >>> its GISA. >>> >>> Upon successful completion, kvm_s390_gisc_register() returns the >>> ISC to be used for GIB alert interruptions. A negative return code >>> indicates an error during registration. >>> >>> Theses functions will be used by other adapter types like AP and PCI to >>> request pass-through interruption support. >>> >>> Signed-off-by: Michael Mueller >>> --- >>> arch/s390/include/asm/kvm_host.h | 9 ++++++ >>> arch/s390/kvm/interrupt.c | 66 ++++++++++++++++++++++++++++++++++++++++ >>> 2 files changed, 75 insertions(+) >>> > >>> +int kvm_s390_gisc_register(struct kvm *kvm, u32 gisc) >>> +{ >>> + if (!kvm->arch.gib_in_use) >>> + return -ENODEV; >>> + if (gisc > MAX_ISC) >>> + return -ERANGE; >>> + >>> + spin_lock(&kvm->arch.iam_ref_lock); >>> + if (kvm->arch.iam_ref_count[gisc] == 0) >>> + kvm->arch.iam |= 0x80 >> gisc; >>> + kvm->arch.iam_ref_count[gisc]++; >>> + if (kvm->arch.iam_ref_count[gisc] == 1) >>> + set_iam(kvm->arch.gisa, kvm->arch.iam); >> >> testing the set_iam return value? >> Even it should be fine if the caller works correctly, this is done >> before GISA is ever used. There is a rc but a check here is not required. There are three cases: a) This is the first ISC that gets registered, then the GISA is not in use and IAM is set in the GISA. b) A second ISC gets registered and the GISA is *not* in the alert list. Then the IAM is set here as well. c) A second ISC gets registered and the GISA is in the alert list. Then the IAM is intentionally not set here by set_iam(). It will be restored by get_ipm() with the new IAM value by the gib alert processing code. > > My feeling is that checking the return code is a good idea, even if it > Should Never Fail(tm). > >> >>> + spin_unlock(&kvm->arch.iam_ref_lock); >>> + >>> + return gib->nisc; >>> +} >>> +EXPORT_SYMBOL_GPL(kvm_s390_gisc_register); >>> + >>> +int kvm_s390_gisc_unregister(struct kvm *kvm, u32 gisc) >>> +{ >>> + int rc = 0; >>> + >>> + if (!kvm->arch.gib_in_use) >>> + return -ENODEV; >>> + if (gisc > MAX_ISC) >>> + return -ERANGE; >>> + >>> + spin_lock(&kvm->arch.iam_ref_lock); >>> + if (kvm->arch.iam_ref_count[gisc] == 0) { >>> + rc = -EINVAL; >>> + goto out; >>> + } >>> + kvm->arch.iam_ref_count[gisc]--; >>> + if (kvm->arch.iam_ref_count[gisc] == 0) { >>> + kvm->arch.iam &= ~(0x80 >> gisc); >>> + set_iam(kvm->arch.gisa, kvm->arch.iam); > > Any chance of this function failing here? If yes, would there be any > implications? It is the same here. > >>> + } >>> +out: >>> + spin_unlock(&kvm->arch.iam_ref_lock); >>> + >>> + return rc; >>> +} >>> +EXPORT_SYMBOL_GPL(kvm_s390_gisc_unregister); >>> + >>> void kvm_s390_gib_destroy(void) >>> { >>> if (!gib) >>> >> >> >