From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941278AbcIHNH3 (ORCPT ); Thu, 8 Sep 2016 09:07:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60415 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932277AbcIHNH1 (ORCPT ); Thu, 8 Sep 2016 09:07:27 -0400 From: Prarit Bhargava To: linux-kernel@vger.kernel.org Cc: Prarit Bhargava , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Len Brown , "Peter Zijlstra (Intel)" , Borislav Petkov , Adrian Hunter , "Christopher S. Hall" , David Woodhouse , kvm@vger.kernel.org Subject: [PATCH] x86, clock: Fix kvm guest tsc initialization Date: Thu, 8 Sep 2016 09:07:18 -0400 Message-Id: <1473340038-26432-1-git-send-email-prarit@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 08 Sep 2016 13:07:27 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When booting a kvm guest on AMD with the latest kernel the following messages are displayed in the boot log: tsc: Unable to calibrate against PIT tsc: HPET/PMTIMER calibration failed aa297292d708 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via CPUID") introduced a change to account for a difference in cpu and tsc frequencies for Intel SKL processors. Before this change the native tsc set x86_platform.calibrate_tsc to native_calibrate_tsc() which is a hardware calibration of the tsc, and in tsc_init() executed tsc_khz = x86_platform.calibrate_tsc(); cpu_khz = tsc_khz; The kvm code changed x86_platform.calibrate_tsc to kvm_get_tsc_khz() and executed the same tsc_init() function. This meant that KVM guests did not execute the native hardware calibration function. After aa297292d708, there are separate native calibrations for cpu_khz and tsc_khz. The code sets x86_platform.calibrate_tsc to native_calibrate_tsc() which is now an Intel specific calibration function , and x86_platform.calibrate_cpu to native_calibrate_cpu() which is the "old" native_calibrate_tsc() function (ie, the native hardware calibration function). tsc_init() now does cpu_khz = x86_platform.calibrate_cpu(); tsc_khz = x86_platform.calibrate_tsc(); if (tsc_khz == 0) tsc_khz = cpu_khz; else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz) cpu_khz = tsc_khz; The kvm code should not call the hardware initialization in native_calibrate_cpu(), as it isn't applicable for kvm and it didn't do that prior to aa297292d708. Setting x86_platform.calibrate_cpu to NULL is not appropriate as cpu_khz_from_cpuid() must be called to get the correct value of cpu_khz on Intel KVM guests. This patch resolves this issue by setting x86_platform.calibrate_cpu to cpu_khz_from_cpuid() for KVM guests, which allows Intel KVM guests to get the right cpu frequency. Fixes: aa297292d708 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via CPUID") Signed-off-by: Prarit Bhargava Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: Len Brown Cc: "Peter Zijlstra (Intel)" Cc: Borislav Petkov Cc: Adrian Hunter Cc: "Christopher S. Hall" Cc: David Woodhouse Cc: kvm@vger.kernel.org --- arch/x86/include/asm/tsc.h | 1 + arch/x86/kernel/kvmclock.c | 1 + arch/x86/kernel/tsc.c | 2 +- 3 files changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h index 33b6365c22fe..1bfb3a14dad0 100644 --- a/arch/x86/include/asm/tsc.h +++ b/arch/x86/include/asm/tsc.h @@ -37,6 +37,7 @@ extern int unsynchronized_tsc(void); extern int check_tsc_unstable(void); extern unsigned long native_calibrate_cpu(void); extern unsigned long native_calibrate_tsc(void); +extern unsigned long cpu_khz_from_cpuid(void); extern unsigned long long native_sched_clock_from_tsc(u64 tsc); extern int tsc_clocksource_reliable; diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 1d39bfbd26bb..1fe23cff7c3e 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -289,6 +289,7 @@ void __init kvmclock_init(void) put_cpu(); x86_platform.calibrate_tsc = kvm_get_tsc_khz; + x86_platform.calibrate_cpu = cpu_khz_from_cpuid; x86_platform.get_wallclock = kvm_get_wallclock; x86_platform.set_wallclock = kvm_set_wallclock; #ifdef CONFIG_X86_LOCAL_APIC diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 78b9cb5a26af..9265ea8effe9 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -699,7 +699,7 @@ unsigned long native_calibrate_tsc(void) return crystal_khz * ebx_numerator / eax_denominator; } -static unsigned long cpu_khz_from_cpuid(void) +unsigned long cpu_khz_from_cpuid(void) { unsigned int eax_base_mhz, ebx_max_mhz, ecx_bus_mhz, edx; -- 1.7.9.3