From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754839Ab2K1MyZ (ORCPT ); Wed, 28 Nov 2012 07:54:25 -0500 Received: from e23smtp01.au.ibm.com ([202.81.31.143]:41413 "EHLO e23smtp01.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754232Ab2K1MyY (ORCPT ); Wed, 28 Nov 2012 07:54:24 -0500 Message-ID: <50B60976.7020905@linux.vnet.ibm.com> Date: Wed, 28 Nov 2012 20:54:14 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120911 Thunderbird/15.0.1 MIME-Version: 1.0 To: Xiao Guangrong CC: Avi Kivity , Marcelo Tosatti , Gleb Natapov , LKML , KVM Subject: [PATCH 2/2] KVM: VMX: fix memory order between loading vmcs and clearing vmcs References: <50B6093B.7040404@linux.vnet.ibm.com> In-Reply-To: <50B6093B.7040404@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit x-cbid: 12112812-1618-0000-0000-000002EFEA1A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org vmcs->cpu indicates whether it exists on the target cpu, -1 means the vmcs does not exist on any vcpu If vcpu load vmcs with vmcs.cpu = -1, it can be directly added to cpu's percpu list. The list can be corrupted if the cpu prefetch the vmcs's list before reading vmcs->cpu. Meanwhile, we should remove vmcs from the list before making vmcs->vcpu == -1 be visible Signed-off-by: Xiao Guangrong --- arch/x86/kvm/vmx.c | 17 +++++++++++++++++ 1 files changed, 17 insertions(+), 0 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 29e8f42..6056d88 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1002,6 +1002,15 @@ static void __loaded_vmcs_clear(void *arg) if (per_cpu(current_vmcs, cpu) == loaded_vmcs->vmcs) per_cpu(current_vmcs, cpu) = NULL; list_del(&loaded_vmcs->loaded_vmcss_on_cpu_link); + + /* + * we should ensure updating loaded_vmcs->loaded_vmcss_on_cpu_link + * is before setting loaded_vmcs->vcpu to -1 which is done in + * loaded_vmcs_init. Otherwise, other cpu can see vcpu = -1 fist + * then adds the vmcs into percpu list before it is deleted. + */ + smp_wmb(); + loaded_vmcs_init(loaded_vmcs); } @@ -1537,6 +1546,14 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu); local_irq_disable(); + + /* + * Read loaded_vmcs->cpu should be before fetching + * loaded_vmcs->loaded_vmcss_on_cpu_link. + * See the comments in __loaded_vmcs_clear(). + */ + smp_rmb(); + list_add(&vmx->loaded_vmcs->loaded_vmcss_on_cpu_link, &per_cpu(loaded_vmcss_on_cpu, cpu)); local_irq_enable(); -- 1.7.7.6