Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932677AbaKMK4f (ORCPT ); Thu, 13 Nov 2014 05:56:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57146 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932364AbaKMK4e (ORCPT ); Thu, 13 Nov 2014 05:56:34 -0500 Message-ID: <54648E53.9080309@redhat.com> Date: Thu, 13 Nov 2014 11:56:19 +0100 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Chris J Arges , kvm@vger.kernel.org CC: Joerg Roedel , Gleb Natapov , linux-kernel@vger.kernel.org Subject: Re: [PATCH] kvm: svm: move WARN_ON in svm_adjust_tsc_offset References: <1415847657-22178-1-git-send-email-chris.j.arges@canonical.com> In-Reply-To: <1415847657-22178-1-git-send-email-chris.j.arges@canonical.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/11/2014 04:00, Chris J Arges wrote: > When running the tsc_adjust kvm-unit-test on an AMD processor with the > IA32_TSC_ADJUST feature enabled, the WARN_ON in svm_adjust_tsc_offset can be > triggered. This WARN_ON checks for a negative adjustment in case __scale_tsc > is called; however it may trigger unnecessary warnings. > > This patch moves the WARN_ON to trigger only if __scale_tsc will actually be > called from svm_adjust_tsc_offset. In addition make adj in kvm_set_msr_common > s64 since this can have signed values. > > Signed-off-by: Chris J Arges > --- > arch/x86/kvm/svm.c | 8 +++++--- > arch/x86/kvm/x86.c | 2 +- > 2 files changed, 6 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index d4f3aaa..6b411ad 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -1056,9 +1056,11 @@ static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool ho > { > struct vcpu_svm *svm = to_svm(vcpu); > > - WARN_ON(adjustment < 0); > - if (host) > - adjustment = svm_scale_tsc(vcpu, adjustment); > + if (host) { > + if (svm->tsc_ratio != TSC_RATIO_DEFAULT) > + WARN_ON(adjustment < 0); > + adjustment = svm_scale_tsc(vcpu, (u64)adjustment); > + } > > svm->vmcb->control.tsc_offset += adjustment; > if (is_guest_mode(vcpu)) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index f85da5c..1cd1376 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -2141,7 +2141,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > case MSR_IA32_TSC_ADJUST: > if (guest_cpuid_has_tsc_adjust(vcpu)) { > if (!msr_info->host_initiated) { > - u64 adj = data - vcpu->arch.ia32_tsc_adjust_msr; > + s64 adj = data - vcpu->arch.ia32_tsc_adjust_msr; > kvm_x86_ops->adjust_tsc_offset(vcpu, adj, true); > } > vcpu->arch.ia32_tsc_adjust_msr = data; > Applied, thanks! Paolo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/