From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gerhard Wiesinger Subject: [PATCH] Fixed KVM problems with old DOS programs. Compatibility can be forced by module parameter. Date: Wed, 4 Nov 2015 20:33:17 +0100 Message-ID: <563A5D7D.4080201@wiesinger.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from vps01.wiesinger.com ([46.36.37.179]:36084 "EHLO vps01.wiesinger.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755032AbbKDTic (ORCPT ); Wed, 4 Nov 2015 14:38:32 -0500 Received: from wiesinger.com (wiesinger.com [62.178.19.14]) by vps01.wiesinger.com (Postfix) with ESMTPS id C8F2D9F21A for ; Wed, 4 Nov 2015 20:33:21 +0100 (CET) Received: from [192.168.0.14] ([192.168.0.14]) (authenticated bits=0) by wiesinger.com (8.15.2/8.15.2) with ESMTPSA id tA4JXHRb031571 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NO) for ; Wed, 4 Nov 2015 20:33:18 +0100 Sender: kvm-owner@vger.kernel.org List-ID: Signed-off-by: Gerhard Wiesinger --- arch/x86/kvm/svm.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 2f9ed1f..e0b00fc 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -198,6 +198,10 @@ static bool npt_enabled; static int npt = true; module_param(npt, int, S_IRUGO); +/* allow backward compatibility with e.g. old DOS application */ +static int npt_task_switch_emulation = true; +module_param(npt_task_switch_emulation, int, S_IRUGO); + /* allow nested virtualization in KVM/SVM */ static int nested = true; module_param(nested, int, S_IRUGO); @@ -1177,6 +1181,9 @@ static void init_vmcb(struct vcpu_svm *svm, bool init_event) if (npt_enabled) { /* Setup VMCB for Nested Paging */ control->nested_ctl = 1; + if (!npt_task_switch_emulation) { + clr_intercept(svm, INTERCEPT_TASK_SWITCH); + } clr_intercept(svm, INTERCEPT_INVLPG); clr_exception_intercept(svm, PF_VECTOR); clr_cr_intercept(svm, INTERCEPT_CR3_READ); -- 2.4.3