From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753959Ab0LGXai (ORCPT ); Tue, 7 Dec 2010 18:30:38 -0500 Received: from canuck.infradead.org ([134.117.69.58]:50375 "EHLO canuck.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751815Ab0LGXah convert rfc822-to-8bit (ORCPT ); Tue, 7 Dec 2010 18:30:37 -0500 Subject: Re: perf hw in kexeced kernel broken in tip From: Peter Zijlstra To: Don Zickus Cc: "Eric W. Biederman" , Vivek Goyal , Yinghai Lu , Ingo Molnar , Jason Wessel , "linux-kernel@vger.kernel.org" , Haren Myneni In-Reply-To: <20101202161502.GL18100@redhat.com> References: <1291219906.32004.1671.camel@laptop> <20101201162335.GB2511@redhat.com> <1291232292.32004.1969.camel@laptop> <20101201194644.GD2511@redhat.com> <1291232989.32004.1987.camel@laptop> <20101201195835.GE2511@redhat.com> <1291234036.32004.2008.camel@laptop> <20101202052321.GH18100@redhat.com> <1291275270.4023.20.camel@twins> <20101202161502.GL18100@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Wed, 08 Dec 2010 00:30:20 +0100 Message-ID: <1291764620.2032.1293.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2010-12-02 at 11:15 -0500, Don Zickus wrote: > Vivek suggested to me this morning that I should just blantantly disable the > perf counter during init when running my test. Nah, we should actively scan for that during the bring-up and kill hw-perf when we find an enable bit set, some BIOSes actively use the PMU, this is something that should be discouraged. --- arch/x86/kernel/cpu/perf_event.c | 30 +++++++++++++++++++++++++++--- 1 files changed, 27 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 817d2b1..7f92833 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -375,15 +375,40 @@ static void release_pmc_hardware(void) {} static bool check_hw_exists(void) { u64 val, val_new = 0; - int ret = 0; + int i, reg, ret = 0; val = 0xabcdUL; ret |= checking_wrmsrl(x86_pmu.perfctr, val); ret |= rdmsrl_safe(x86_pmu.perfctr, &val_new); - if (ret || val != val_new) + if (ret || val != val_new) { + printk(KERN_CONT "Broken PMU hardware detected, software events only.\n"); return false; + } + + /* + * Check to see if the BIOS enabled any of the counters, if so + * complain and bail. + */ + for (i = 0; i < x86_pmu.num_counters; i++) { + reg = x86_pmu.eventsel + i; + rdmsrl(reg, val); + if (val & ARCH_PERFMON_EVENTSEL_ENABLE) + goto bios_fail; + } + + for (i = 0; i < x86_pmu.num_counters_fixed; i++) { + reg = MSR_ARCH_PERFMON_FIXED_CTR_CTRL; + rdmsrl(reg, val); + if (val & (0x03 << i*4)) + goto bios_fail; + } return true; + +bios_fail: + printk(KERN_CONT "Broken BIOS detected, software events only.\n"); + printk(KERN_ERR FW_BUG "invalid MSR %x=%Lx\n", reg, val); + return false; } static void reserve_ds_buffers(void); @@ -1379,7 +1404,6 @@ int __init init_hw_perf_events(void) /* sanity check that the hardware exists or is emulated */ if (!check_hw_exists()) { - pr_cont("Broken PMU hardware detected, software events only.\n"); return 0; } > Looking through the code I > don't think I can do this using disable_all because some routines look for > the active bit to be set and some arches have different disable registers > than others. Thoughts? Something like the below, preferably I'd key that off of SYS_KEXEC, but looking through the existing notifiers adding a state requires touching all of them :/ --- kernel/perf_event.c | 21 +++++++++++++++++++++ 1 files changed, 21 insertions(+), 0 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 195393c..7abcd8d 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -6383,6 +6384,25 @@ static void perf_event_exit_cpu(int cpu) static inline void perf_event_exit_cpu(int cpu) { } #endif +static int +perf_reboot(struct notifier_block *notifier, unsigned long val, void *v) +{ + /* + * XXX this relies on hotplug, does kexec do too? + */ + perf_event_exit_cpu(0); + return NOTIFY_OK; +} + +/* + * Run the perf reboot notifier at the very last possible moment so that + * the generic watchdog code runs as long as possible. + */ +static struct notifier_block perf_reboot_notifier = { + .notifier_call = perf_reboot, + .priority = INT_MIN, +}; + static int __cpuinit perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { @@ -6418,6 +6438,7 @@ void __init perf_event_init(void) perf_pmu_register(&perf_task_clock); perf_tp_register(); perf_cpu_notifier(perf_cpu_notify); + register_reboot_notifier(&perf_reboot_notifier); ret = init_hw_breakpoint(); WARN(ret, "hw_breakpoint initialization failed with: %d", ret);