From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754263AbbG3LkX (ORCPT ); Thu, 30 Jul 2015 07:40:23 -0400 Received: from e06smtp11.uk.ibm.com ([195.75.94.107]:50894 "EHLO e06smtp11.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750879AbbG3LkW (ORCPT ); Thu, 30 Jul 2015 07:40:22 -0400 X-Helo: d06dlp02.portsmouth.uk.ibm.com X-MailFrom: borntraeger@de.ibm.com X-RcptTo: linux-kernel@vger.kernel.org Message-ID: <55BA0D1D.7090002@de.ibm.com> Date: Thu, 30 Jul 2015 13:40:13 +0200 From: Christian Borntraeger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org CC: mtosatti@redhat.com, srutherford@google.com, rkrcmar@redhat.com Subject: Re: [PATCH 2/4] KVM: document memory barriers for kvm->vcpus/kvm->online_vcpus References: <1438176538-26191-1-git-send-email-pbonzini@redhat.com> <1438176538-26191-3-git-send-email-pbonzini@redhat.com> In-Reply-To: <1438176538-26191-3-git-send-email-pbonzini@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15073011-0041-0000-0000-00000544757E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 29.07.2015 um 15:28 schrieb Paolo Bonzini: > Signed-off-by: Paolo Bonzini > --- > include/linux/kvm_host.h | 4 ++++ > virt/kvm/kvm_main.c | 2 ++ > 2 files changed, 6 insertions(+) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index bd1097a95704..81089cf1f0c1 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -427,6 +427,10 @@ struct kvm { > > static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i) > { > + /* Pairs with smp_wmb() in kvm_vm_ioctl_create_vcpu, in case > + * the caller has read kvm->online_vcpus before (as is the case > + * for kvm_for_each_vcpu, for example). > + */ > smp_rmb(); Hmmm, wouldnt something like smp_mb__after_atomic > return kvm->vcpus[i]; > } > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 8dc4828f623f..093b3d10b411 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2206,6 +2206,8 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) > } > > kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu; and smp_mb__before_atomic be the better function? > + > + /* Pairs with smp_rmb() in kvm_get_vcpu. */ > smp_wmb(); > atomic_inc(&kvm->online_vcpus); >