From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424525AbcFMOna (ORCPT ); Mon, 13 Jun 2016 10:43:30 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:60956 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1424075AbcFMOn1 (ORCPT ); Mon, 13 Jun 2016 10:43:27 -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 16:43:06 +0200 From: Cornelia Huck To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Christian Borntraeger Subject: Re: [PATCH 1/3] KVM: introduce kvm->created_vcpus In-Reply-To: <1465824332-10628-2-git-send-email-pbonzini@redhat.com> References: <1465824332-10628-1-git-send-email-pbonzini@redhat.com> <1465824332-10628-2-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: 16061314-0020-0000-0000-000001BF27FE X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16061314-0021-0000-0000-00001C53A3B3 Message-Id: <20160613164306.760ba899.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-1606130165 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 13 Jun 2016 15:25:30 +0200 Paolo Bonzini wrote: > The race between creating the irqchip and the first VCPU is > currently fixed by checking the presence of an irqchip before > updating kvm->online_vcpus, and undoing the whole VCPU creation > if someone created the irqchip in the meanwhile. > > Instead, introduce a new field in struct kvm that will count VCPUs > under a mutex, without the atomic access and memory ordering that we > need elsewhere to protect the vcpus array. This also plugs the race > and is more easily applicable in all similar circumstances. > > Signed-off-by: Paolo Bonzini > --- > include/linux/kvm_host.h | 8 ++++++++ > virt/kvm/kvm_main.c | 23 +++++++++++++++++------ > 2 files changed, 25 insertions(+), 6 deletions(-) Reviewed-by: Cornelia Huck