From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934564AbdBQOTJ (ORCPT ); Fri, 17 Feb 2017 09:19:09 -0500 Received: from mx2.suse.de ([195.135.220.15]:59633 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934288AbdBQOTH (ORCPT ); Fri, 17 Feb 2017 09:19:07 -0500 Subject: Re: [PATCH 2/2] x86/xen: use capabilities instead of fake cpuid values To: Boris Ostrovsky , linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, x86@kernel.org References: <20170217073625.13418-1-jgross@suse.com> <20170217073625.13418-3-jgross@suse.com> Cc: hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com From: Juergen Gross Message-ID: <1f923425-47f5-5e6d-5bca-e4c98d54ced5@suse.com> Date: Fri, 17 Feb 2017 15:19:04 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: 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 17/02/17 15:05, Boris Ostrovsky wrote: > > > On 02/17/2017 02:36 AM, Juergen Gross wrote: >> When running as pv domain xen_cpuid() is being used instead of >> native_cpuid(). In xen_cpuid() the aperf/mperf feature is indicated >> as not being present by special casing the related cpuid leaf. >> >> Instead of delivering fake cpuid values clear the cpu capability bit >> for aperf/mperf instead. >> >> Signed-off-by: Juergen Gross >> --- >> arch/x86/xen/enlighten.c | 11 +++-------- >> 1 file changed, 3 insertions(+), 8 deletions(-) >> >> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c >> index 83399ce..0eebb75 100644 >> --- a/arch/x86/xen/enlighten.c >> +++ b/arch/x86/xen/enlighten.c >> @@ -301,9 +301,6 @@ xen_running_on_version_or_later(unsigned int >> major, unsigned int minor) >> return false; >> } >> >> -#define CPUID_THERM_POWER_LEAF 6 >> -#define APERFMPERF_PRESENT 0 >> - >> static __read_mostly unsigned int cpuid_leaf1_edx_mask = ~0; >> static __read_mostly unsigned int cpuid_leaf1_ecx_mask = ~0; >> >> @@ -337,11 +334,6 @@ static void xen_cpuid(unsigned int *ax, unsigned >> int *bx, >> *dx = cpuid_leaf5_edx_val; >> return; >> >> - case CPUID_THERM_POWER_LEAF: >> - /* Disabling APERFMPERF for kernel usage */ >> - maskecx = ~(1 << APERFMPERF_PRESENT); >> - break; >> - > > > But now APERF/MPERF will be reported as supported by CPUID, won't it? Yes. But this shouldn't be a problem as the kernel is always testing X86_FEATURE_APERFMPERF for testing the support. >> case 0xb: >> /* Suppress extended topology stuff */ >> maskebx = 0; >> @@ -462,6 +454,9 @@ static void __init xen_init_cpuid_mask(void) >> if (xen_check_mwait()) >> cpuid_leaf1_ecx_set_mask = (1 << (X86_FEATURE_MWAIT % 32)); >> >> + /* Disable APERFMPERF feature. */ >> + setup_clear_cpu_cap(X86_FEATURE_APERFMPERF); >> + >> /* Disable DCA feature. */ >> setup_clear_cpu_cap(X86_FEATURE_DCA); > > > I think both of those can go to xen_set_cpu_features(). Okay. I'll move them. I think we can convert some of the remaining cpuid bit modifications to cpu capabilities as well. Juergen