From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424561AbcFMOoj (ORCPT ); Mon, 13 Jun 2016 10:44:39 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:22307 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1424322AbcFMOoh (ORCPT ); Mon, 13 Jun 2016 10:44:37 -0400 X-IBM-Helo: d06dlp03.portsmouth.uk.ibm.com X-IBM-MailFrom: cornelia.huck@de.ibm.com X-IBM-RcptTo: kvm@vger.kernel.org;linux-kernel@vger.kernel.org Date: Mon, 13 Jun 2016 16:44:21 +0200 From: Cornelia Huck To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Christian Borntraeger Subject: Re: [PATCH 0/3] KVM: do not use kvm->online_vcpus to check "has one VCPU been created?" In-Reply-To: <1465824332-10628-1-git-send-email-pbonzini@redhat.com> References: <1465824332-10628-1-git-send-email-pbonzini@redhat.com> Organization: IBM Deutschland Research & Development GmbH Vorsitzende des Aufsichtsrats: Martina Koederitz =?UTF-8?B?R2VzY2jDpGZ0c2bDvGhydW5nOg==?= Dirk Wittkopp Sitz der Gesellschaft: =?UTF-8?B?QsO2Ymxpbmdlbg==?= Registergericht: Amtsgericht Stuttgart, HRB 243294 X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16061314-0028-0000-0000-000001D6273F X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16061314-0029-0000-0000-00001F34A031 Message-Id: <20160613164421.77b70bee.cornelia.huck@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-06-13_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1606130166 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 13 Jun 2016 15:25:29 +0200 Paolo Bonzini wrote: > kvm->online_vcpus is only updated at the very end of KVM_CREATE_VCPU. > Thus, it can be racy to use it as a check for "has any VCPU been created > already?". While x86 detects the race through kvm_vcpu_compatible, > it is kinda hackish and s390 does not do anything similar. Provide a > better fix for both. > > Paolo Bonzini (3): > KVM: introduce created_vcpus > KVM: remove kvm_vcpu_compatible > KVM: s390: use created_vcpus > > arch/s390/kvm/kvm-s390.c | 10 +++++----- > arch/x86/kvm/Kconfig | 1 - > arch/x86/kvm/x86.c | 11 +++-------- > include/linux/kvm_host.h | 14 ++++++++------ > virt/kvm/Kconfig | 3 --- > virt/kvm/kvm_main.c | 27 +++++++++++++++++---------- > 6 files changed, 33 insertions(+), 33 deletions(-) > Looks like a sane approach, only two inversions in the s390 patch :)