From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT Date: Sun, 12 Aug 2012 16:25:23 +0300 Message-ID: <20120812132523.GM3341@redhat.com> References: <20120812131228.GL3341@redhat.com> <5027AE33.1040408@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org, mtosatti@redhat.com To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:58251 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751755Ab2HLNZZ (ORCPT ); Sun, 12 Aug 2012 09:25:25 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q7CDPP5r021211 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Sun, 12 Aug 2012 09:25:25 -0400 Content-Disposition: inline In-Reply-To: <5027AE33.1040408@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Aug 12, 2012 at 04:22:59PM +0300, Avi Kivity wrote: > On 08/12/2012 04:12 PM, Gleb Natapov wrote: > > MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT. Restore it to the correct > > value. > > > > @@ -6222,6 +6222,7 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx) > > static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) > > { > > struct vcpu_vmx *vmx = to_vmx(vcpu); > > + unsigned long debugctlmsr; > > > > if (is_guest_mode(vcpu) && !vmx->nested.nested_run_pending) { > > struct vmcs12 *vmcs12 = get_vmcs12(vcpu); > > @@ -6261,6 +6262,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) > > vmx_set_interrupt_shadow(vcpu, 0); > > > > atomic_switch_perf_msrs(vmx); > > + debugctlmsr = get_debugctlmsr(); > > How expensive is this? We may want a follow-on patch to cache it in a > per-cpu variable. > I have patches ready. I couldn't measure any overhead of the rdmsr(MSR_IA32_DEBUGCTLMSR). -- Gleb.