From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751815AbaJORMR (ORCPT ); Wed, 15 Oct 2014 13:12:17 -0400 Received: from mail-pa0-f53.google.com ([209.85.220.53]:32839 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751643AbaJORMQ (ORCPT ); Wed, 15 Oct 2014 13:12:16 -0400 From: Andy Lutomirski To: x86@kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner Cc: Bandan Das , Andy Lutomirski , stable@vger.kernel.org Subject: [PATCH] x86, apic: Handle a bad TSC more gracefully Date: Wed, 15 Oct 2014 10:12:07 -0700 Message-Id: X-Mailer: git-send-email 1.9.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If the TSC is unusable or disabled, then this patch fixes: - Confusion while trying to clear old APIC interrupts. - Division by zero and incorrect programming of the TSC deadline timer. This fixes boot if the CPU has a TSC deadline timer but a missing or broken TSC. The failure to boot can be observed with qemu using -cpu qemu64,-tsc,+tsc-deadline This also happens to me in nested KVM for unknown reasons. With this patch, I can boot cleanly (although without a TSC). Cc: stable@vger.kernel.org Signed-off-by: Andy Lutomirski --- arch/x86/kernel/apic/apic.c | 4 ++-- arch/x86/kernel/tsc.c | 5 ++++- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 67760275544b..24b5894396a0 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1297,7 +1297,7 @@ void setup_local_APIC(void) unsigned int value, queued; int i, j, acked = 0; unsigned long long tsc = 0, ntsc; - long long max_loops = cpu_khz; + long long max_loops = cpu_khz ? cpu_khz : 1000000; if (cpu_has_tsc) rdtscll(tsc); @@ -1383,7 +1383,7 @@ void setup_local_APIC(void) break; } if (queued) { - if (cpu_has_tsc) { + if (cpu_has_tsc && cpu_khz) { rdtscll(ntsc); max_loops = (cpu_khz << 10) - (ntsc - tsc); } else diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index b6025f9e36c6..b7e50bba3bbb 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1166,14 +1166,17 @@ void __init tsc_init(void) x86_init.timers.tsc_pre_init(); - if (!cpu_has_tsc) + if (!cpu_has_tsc) { + setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER); return; + } tsc_khz = x86_platform.calibrate_tsc(); cpu_khz = tsc_khz; if (!tsc_khz) { mark_tsc_unstable("could not calculate TSC khz"); + setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER); return; } -- 1.9.3