Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755753AbcCNSFK (ORCPT ); Mon, 14 Mar 2016 14:05:10 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:43793 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754261AbcCNRya (ORCPT ); Mon, 14 Mar 2016 13:54:30 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Marcelo Tosatti , David Matlack , Paolo Bonzini Subject: [PATCH 3.14 10/19] KVM: x86: move steal time initialization to vcpu entry time Date: Mon, 14 Mar 2016 10:52:50 -0700 Message-Id: <20160314175029.865433879@linuxfoundation.org> X-Mailer: git-send-email 2.7.2 In-Reply-To: <20160314175029.541742468@linuxfoundation.org> References: <20160314175029.541742468@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1659 Lines: 61 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Marcelo Tosatti commit 7cae2bedcbd4680b155999655e49c27b9cf020fa upstream. As reported at https://bugs.launchpad.net/qemu/+bug/1494350, it is possible to have vcpu->arch.st.last_steal initialized from a thread other than vcpu thread, say the iothread, via KVM_SET_MSRS. Which can cause an overflow later (when subtracting from vcpu threads sched_info.run_delay). To avoid that, move steal time accumulation to vcpu entry time, before copying steal time data to guest. Signed-off-by: Marcelo Tosatti Reviewed-by: David Matlack Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1991,6 +1991,8 @@ static void accumulate_steal_time(struct static void record_steal_time(struct kvm_vcpu *vcpu) { + accumulate_steal_time(vcpu); + if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED)) return; @@ -2123,12 +2125,6 @@ int kvm_set_msr_common(struct kvm_vcpu * if (!(data & KVM_MSR_ENABLED)) break; - vcpu->arch.st.last_steal = current->sched_info.run_delay; - - preempt_disable(); - accumulate_steal_time(vcpu); - preempt_enable(); - kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); break; @@ -2818,7 +2814,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu vcpu->cpu = cpu; } - accumulate_steal_time(vcpu); kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); }