Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966252AbcDLVXO (ORCPT ); Tue, 12 Apr 2016 17:23:14 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:50904 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030205AbcDLUyI (ORCPT ); Tue, 12 Apr 2016 16:54:08 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Marcelo Tosatti , Paolo Bonzini , Liang Chen , Luis Henriques , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 57/70] KVM: x86: move steal time initialization to vcpu entry time Date: Tue, 12 Apr 2016 13:52:42 -0700 Message-Id: <1460494375-30070-58-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1460494375-30070-1-git-send-email-kamal@canonical.com> References: <1460494375-30070-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1957 Lines: 65 4.2.8-ckt8 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ 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 Cc: Liang Chen Signed-off-by: Luis Henriques Signed-off-by: Kamal Mostafa --- arch/x86/kvm/x86.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 382a150..cefcb02 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2032,6 +2032,8 @@ static void accumulate_steal_time(struct kvm_vcpu *vcpu) static void record_steal_time(struct kvm_vcpu *vcpu) { + accumulate_steal_time(vcpu); + if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED)) return; @@ -2184,12 +2186,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 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; @@ -2834,7 +2830,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) vcpu->cpu = cpu; } - accumulate_steal_time(vcpu); kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); } -- 2.7.4