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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8340BC38142 for ; Fri, 27 Jan 2023 14:20:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232450AbjA0OUI (ORCPT ); Fri, 27 Jan 2023 09:20:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33682 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232398AbjA0OUH (ORCPT ); Fri, 27 Jan 2023 09:20:07 -0500 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50CCA7F333; Fri, 27 Jan 2023 06:20:06 -0800 (PST) Received: from pps.filterd (m0187473.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 30RDfmLf028778; Fri, 27 Jan 2023 14:20:06 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : in-reply-to : references : mime-version : content-type : content-transfer-encoding; s=pp1; bh=mlc8bOGmiF+UCQlzByWHBk1Tm1LFws7GM4zIMlhHcBI=; b=HPjvo50bt7xCTPLidNiL6sxFsDbIyqbLNLxGBJmNWVuaOpBv331PVMa5x+3vPzZanS4u AcTBJLG6qmQdKRRahir0msWizqk3vvpiYbUy4cDWI0GkWcF5sIo/MoxLOjViOM+Xc8rM NGVx+t2dZ2bH8lzcEQMrGlk0QJ8M6sMeLbqpgJnuNCfPqX6Oip9ehsarJZXWa91YC2mS MRTdg4VNLb9QZlVZNYvP/KmmXVmdYa83dXz+XDUP1x7n9/X1FJ7lnOXINNOm+vVdZJJ7 RpoqkI0MlqiwUSEbpS1Yn0abaTAKFEeloiizm5NM0XxW5cb8Xz9L10jOwOPCtd4JnOLz 6w== Received: from ppma02fra.de.ibm.com (47.49.7a9f.ip4.static.sl-reverse.com [159.122.73.71]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3ncfqk95hq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 27 Jan 2023 14:20:05 +0000 Received: from pps.filterd (ppma02fra.de.ibm.com [127.0.0.1]) by ppma02fra.de.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 30RBJQnc031519; Fri, 27 Jan 2023 14:20:03 GMT Received: from smtprelay02.fra02v.mail.ibm.com ([9.218.2.226]) by ppma02fra.de.ibm.com (PPS) with ESMTPS id 3n87p6dg2x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 27 Jan 2023 14:20:03 +0000 Received: from smtpav07.fra02v.mail.ibm.com (smtpav07.fra02v.mail.ibm.com [10.20.54.106]) by smtprelay02.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 30REJxlH48038342 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 27 Jan 2023 14:19:59 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B80102004B; Fri, 27 Jan 2023 14:19:59 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2524B20043; Fri, 27 Jan 2023 14:19:59 +0000 (GMT) Received: from p-imbrenda (unknown [9.171.87.61]) by smtpav07.fra02v.mail.ibm.com (Postfix) with SMTP; Fri, 27 Jan 2023 14:19:59 +0000 (GMT) Date: Fri, 27 Jan 2023 15:19:57 +0100 From: Claudio Imbrenda To: Nico Boehr Cc: borntraeger@linux.ibm.com, frankja@linux.ibm.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH v4 1/1] KVM: s390: disable migration mode when dirty tracking is disabled Message-ID: <20230127151957.09a1c0bc@p-imbrenda> In-Reply-To: <20230127140532.230651-2-nrb@linux.ibm.com> References: <20230127140532.230651-1-nrb@linux.ibm.com> <20230127140532.230651-2-nrb@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 4.1.1 (GTK 3.24.35; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: imnW-DO7fkIEdaLfakdOPFYr1jZtfqWu X-Proofpoint-ORIG-GUID: imnW-DO7fkIEdaLfakdOPFYr1jZtfqWu X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.122.1 definitions=2023-01-27_08,2023-01-27_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 adultscore=0 phishscore=0 malwarescore=0 mlxscore=0 mlxlogscore=999 spamscore=0 clxscore=1015 impostorscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2301270133 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Fri, 27 Jan 2023 15:05:32 +0100 Nico Boehr wrote: > Migration mode is a VM attribute which enables tracking of changes in > storage attributes (PGSTE). It assumes dirty tracking is enabled on all > memslots to keep a dirty bitmap of pages with changed storage attributes. > > When enabling migration mode, we currently check that dirty tracking is > enabled for all memslots. However, userspace can disable dirty tracking > without disabling migration mode. > > Since migration mode is pointless with dirty tracking disabled, disable > migration mode whenever userspace disables dirty tracking on any slot. > > Also update the documentation to clarify that dirty tracking must be > enabled when enabling migration mode, which is already enforced by the > code in kvm_s390_vm_start_migration(). > > Also highlight in the documentation for KVM_S390_GET_CMMA_BITS that it > can now fail with -EINVAL when dirty tracking is disabled while > migration mode is on. Move all the error codes to a table to this stays > readable. > > To disable migration mode, slots_lock should be held, which is taken > in kvm_set_memory_region() and thus held in > kvm_arch_prepare_memory_region(). > > Restructure the prepare code a bit so all the sanity checking is done > before disabling migration mode. This ensures migration mode isn't > disabled when some sanity check fails. > > Cc: stable@vger.kernel.org > Fixes: 190df4a212a7 ("KVM: s390: CMMA tracking, ESSA emulation, migration mode") > Signed-off-by: Nico Boehr Reviewed-by: Claudio Imbrenda > --- > Documentation/virt/kvm/api.rst | 16 ++++++---- > Documentation/virt/kvm/devices/vm.rst | 4 +++ > arch/s390/kvm/kvm-s390.c | 43 +++++++++++++++++++-------- > 3 files changed, 45 insertions(+), 18 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 9807b05a1b57..2978acfcafc4 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -4537,11 +4537,17 @@ mask is unused. > > values points to the userspace buffer where the result will be stored. > > -This ioctl can fail with -ENOMEM if not enough memory can be allocated to > -complete the task, with -ENXIO if CMMA is not enabled, with -EINVAL if > -KVM_S390_CMMA_PEEK is not set but migration mode was not enabled, with > --EFAULT if the userspace address is invalid or if no page table is > -present for the addresses (e.g. when using hugepages). > +Errors: > + > + ====== ============================================================= > + ENOMEM not enough memory can be allocated to complete the task > + ENXIO if CMMA is not enabled > + EINVAL if KVM_S390_CMMA_PEEK is not set but migration mode was not enabled > + EINVAL if KVM_S390_CMMA_PEEK is not set but dirty tracking has been > + disabled (and thus migration mode was automatically disabled) > + EFAULT if the userspace address is invalid or if no page table is > + present for the addresses (e.g. when using hugepages). > + ====== ============================================================= > > 4.108 KVM_S390_SET_CMMA_BITS > ---------------------------- > diff --git a/Documentation/virt/kvm/devices/vm.rst b/Documentation/virt/kvm/devices/vm.rst > index 60acc39e0e93..147efec626e5 100644 > --- a/Documentation/virt/kvm/devices/vm.rst > +++ b/Documentation/virt/kvm/devices/vm.rst > @@ -302,6 +302,10 @@ Allows userspace to start migration mode, needed for PGSTE migration. > Setting this attribute when migration mode is already active will have > no effects. > > +Dirty tracking must be enabled on all memslots, else -EINVAL is returned. When > +dirty tracking is disabled on any memslot, migration mode is automatically > +stopped. > + > :Parameters: none > :Returns: -ENOMEM if there is not enough free memory to start migration mode; > -EINVAL if the state of the VM is invalid (e.g. no memory defined); > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index e4890e04b210..cb72f9a09fb3 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -5633,23 +5633,40 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, > if (kvm_s390_pv_get_handle(kvm)) > return -EINVAL; > > - if (change == KVM_MR_DELETE || change == KVM_MR_FLAGS_ONLY) > - return 0; > + if (change != KVM_MR_DELETE && change != KVM_MR_FLAGS_ONLY) { > + /* > + * A few sanity checks. We can have memory slots which have to be > + * located/ended at a segment boundary (1MB). The memory in userland is > + * ok to be fragmented into various different vmas. It is okay to mmap() > + * and munmap() stuff in this slot after doing this call at any time > + */ > > - /* A few sanity checks. We can have memory slots which have to be > - located/ended at a segment boundary (1MB). The memory in userland is > - ok to be fragmented into various different vmas. It is okay to mmap() > - and munmap() stuff in this slot after doing this call at any time */ > + if (new->userspace_addr & 0xffffful) > + return -EINVAL; > > - if (new->userspace_addr & 0xffffful) > - return -EINVAL; > + size = new->npages * PAGE_SIZE; > + if (size & 0xffffful) > + return -EINVAL; > > - size = new->npages * PAGE_SIZE; > - if (size & 0xffffful) > - return -EINVAL; > + if ((new->base_gfn * PAGE_SIZE) + size > kvm->arch.mem_limit) > + return -EINVAL; > + } > > - if ((new->base_gfn * PAGE_SIZE) + size > kvm->arch.mem_limit) > - return -EINVAL; > + if (!kvm->arch.migration_mode) > + return 0; > + > + /* > + * Turn off migration mode when: > + * - userspace creates a new memslot with dirty logging off, > + * - userspace modifies an existing memslot (MOVE or FLAGS_ONLY) and > + * dirty logging is turned off. > + * Migration mode expects dirty page logging being enabled to store > + * its dirty bitmap. > + */ > + if (change != KVM_MR_DELETE && > + !(new->flags & KVM_MEM_LOG_DIRTY_PAGES)) > + WARN(kvm_s390_vm_stop_migration(kvm), > + "Failed to stop migration mode"); > > return 0; > }