From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753771AbdKMQYI (ORCPT ); Mon, 13 Nov 2017 11:24:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52698 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753513AbdKMQYG (ORCPT ); Mon, 13 Nov 2017 11:24:06 -0500 Subject: Re: [patch v2 8/8] KVM: x86: Disable intercept for Intel processor trace MSRs To: Luwei Kang , kvm@vger.kernel.org Cc: rkrcmar@redhat.com, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, Chao Peng References: <1509401117-15521-1-git-send-email-luwei.kang@intel.com> <1509401117-15521-9-git-send-email-luwei.kang@intel.com> From: Paolo Bonzini Message-ID: Date: Mon, 13 Nov 2017 17:24:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1509401117-15521-9-git-send-email-luwei.kang@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Mon, 13 Nov 2017 16:24:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/10/2017 23:05, Luwei Kang wrote: > From: Chao Peng > > Pass through Intel processor trace to guest directly. > > Signed-off-by: Chao Peng > Signed-off-by: Luwei Kang > --- > arch/x86/kvm/vmx.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 8f61a8d..01447e2 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -7029,6 +7029,19 @@ static __init int hardware_setup(void) > !cpu_has_vmx_intel_pt() || !cpu_has_vmx_pt_use_gpa()) > pt_mode = PT_MODE_SYSTEM; > > + if (pt_mode == PT_MODE_HOST_GUEST) { > + u32 i, eax, ebx, ecx, edx; > + > + cpuid_count(0x14, 1, &eax, &ebx, &ecx, &edx); > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_STATUS, false); > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_BASE, false); > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_MASK, false); > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_CR3_MATCH, false); > + for (i = 0; i < (eax & 0x7); i++) > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_ADDR0_A + i, > + false); > + } > + As I mentioned earlier, this probably makes vmentry/vmexit too expensive when guests are not using processor tracing. I would do it only if guest TRACEEN=1 (since anyway the values have to be correct if guest TRACEEN=1, and a change in TRACEEN always causes a vmexit). Paolo > return alloc_kvm_area(); > > out: >