From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: [PATCH] KVM: x86: move steal time initialization to vcpu entry time Date: Wed, 14 Oct 2015 19:33:09 -0300 Message-ID: <20151014223309.GA13900@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Rik van Riel , "Dr. David Alan Gilbert" , Paolo Bonzini , Amit Shah To: kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:48432 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753882AbbJNWdg (ORCPT ); Wed, 14 Oct 2015 18:33:36 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 35096C0BFD02 for ; Wed, 14 Oct 2015 22:33:36 +0000 (UTC) Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: 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 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 8f0f6ec..0e0332e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2030,6 +2030,8 @@ 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; @@ -2182,12 +2184,6 @@ 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; @@ -2830,7 +2826,6 @@ 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); }