Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753463AbbHGD2q (ORCPT ); Thu, 6 Aug 2015 23:28:46 -0400 Received: from mga02.intel.com ([134.134.136.20]:2165 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752098AbbHGD2p (ORCPT ); Thu, 6 Aug 2015 23:28:45 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,627,1432623600"; d="scan'208";a="743866505" From: Haozhong Zhang To: kvm@vger.kernel.org Cc: Gleb Natapov , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Haozhong Zhang Subject: [PATCH] KVM: x86: Use adjustment in guest cycles when handling MSR_IA32_TSC_ADJUST Date: Fri, 7 Aug 2015 11:24:32 +0800 Message-Id: <1438917872-23908-1-git-send-email-haozhong.zhang@intel.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1754 Lines: 40 When kvm_set_msr_common() handles a guest's write to MSR_IA32_TSC_ADJUST, it will calcuate an adjustment based on the data written by guest and then use it to adjust TSC offset by calling a call-back adjust_tsc_offset(). The 3rd parameter of adjust_tsc_offset() indicates whether the adjustment is in host TSC cycles or in guest TSC cycles. If SVM TSC scaling is enabled, adjust_tsc_offset() [i.e. svm_adjust_tsc_offset()] will first scale the adjustment; otherwise, it will just use the unscaled one. As the MSR write here comes from the guest, the adjustment is in guest TSC cycles. However, the current kvm_set_msr_common() uses it as a value in host TSC cycles (by using true as the 3rd parameter of adjust_tsc_offset()), which can result in an incorrect adjustment of TSC offset if SVM TSC scaling is enabled. This patch fixes this problem. Signed-off-by: Haozhong Zhang --- arch/x86/kvm/x86.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5ef2560..3cd6cd2 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2105,7 +2105,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) if (guest_cpuid_has_tsc_adjust(vcpu)) { if (!msr_info->host_initiated) { s64 adj = data - vcpu->arch.ia32_tsc_adjust_msr; - kvm_x86_ops->adjust_tsc_offset(vcpu, adj, true); + adjust_tsc_offset_guest(vcpu, adj); } vcpu->arch.ia32_tsc_adjust_msr = data; } -- 1.7.9.5 -- 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/