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Date: Thu, 23 Sep 2021 22:29:31 +0800
From: Pingfan Liu <kernelfans@...il.com>
To: Linux ARM <linux-arm-kernel@...ts.infradead.org>
Cc: Sumit Garg <sumit.garg@...aro.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Marc Zyngier <maz@...nel.org>,
Kees Cook <keescook@...omium.org>,
Masahiro Yamada <masahiroy@...nel.org>,
Sami Tolvanen <samitolvanen@...gle.com>,
Petr Mladek <pmladek@...e.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Wang Qing <wangqing@...o.com>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Santosh Sivaraj <santosh@...six.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 4/4] arm64: Enable perf events based hard lockup detector
On Thu, Sep 23, 2021 at 10:10 PM Pingfan Liu <kernelfans@...il.com> wrote:
>
> From: Sumit Garg <sumit.garg@...aro.org>
>
To Sumit, I think credits should go to you and keep you as the author.
Please let me know if you dislike it.
Thanks,
Pingfan
> With the recent feature added to enable perf events to use pseudo NMIs
> as interrupts on platforms which support GICv3 or later, its now been
> possible to enable hard lockup detector (or NMI watchdog) on arm64
> platforms. So enable corresponding support.
>
> One thing to note here is that normally lockup detector is initialized
> just after the early initcalls but PMU on arm64 comes up much later as
> device_initcall(). So we need to re-initialize lockup detection once
> PMU has been initialized.
>
> [1]: http://lore.kernel.org/linux-arm-kernel/1610712101-14929-1-git-send-email-sumit.garg@linaro.org
>
> Signed-off-by: Sumit Garg <sumit.garg@...aro.org>
> (Pingfan: adapt it to watchdog_hld async model based on [1])
> Signed-off-by: Pingfan Liu <kernelfans@...il.com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Masahiro Yamada <masahiroy@...nel.org>
> Cc: Sami Tolvanen <samitolvanen@...gle.com>
> Cc: Petr Mladek <pmladek@...e.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Wang Qing <wangqing@...o.com>
> Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
> Cc: Santosh Sivaraj <santosh@...six.org>
> Cc: linux-kernel@...r.kernel.org
> To: linux-arm-kernel@...ts.infradead.org
> ---
> arch/arm64/Kconfig | 2 ++
> arch/arm64/kernel/Makefile | 1 +
> arch/arm64/kernel/perf_event.c | 11 ++++++++--
> arch/arm64/kernel/watchdog_hld.c | 36 ++++++++++++++++++++++++++++++++
> drivers/perf/arm_pmu.c | 5 +++++
> include/linux/perf/arm_pmu.h | 2 ++
> 6 files changed, 55 insertions(+), 2 deletions(-)
> create mode 100644 arch/arm64/kernel/watchdog_hld.c
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 5c7ae4c3954b..8287e9e1d28d 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -189,6 +189,8 @@ config ARM64
> select HAVE_NMI
> select HAVE_PATA_PLATFORM
> select HAVE_PERF_EVENTS
> + select HAVE_PERF_EVENTS_NMI if ARM64_PSEUDO_NMI
> + select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
> select HAVE_PERF_REGS
> select HAVE_PERF_USER_STACK_DUMP
> select HAVE_REGS_AND_STACK_ACCESS_API
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 3f1490bfb938..789c2fe5bb90 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -46,6 +46,7 @@ obj-$(CONFIG_MODULES) += module.o
> obj-$(CONFIG_ARM64_MODULE_PLTS) += module-plts.o
> obj-$(CONFIG_PERF_EVENTS) += perf_regs.o perf_callchain.o
> obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o
> +obj-$(CONFIG_HARDLOCKUP_DETECTOR_PERF) += watchdog_hld.o
> obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
> obj-$(CONFIG_CPU_PM) += sleep.o suspend.o
> obj-$(CONFIG_CPU_IDLE) += cpuidle.o
> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
> index b4044469527e..a34343d0f418 100644
> --- a/arch/arm64/kernel/perf_event.c
> +++ b/arch/arm64/kernel/perf_event.c
> @@ -23,6 +23,7 @@
> #include <linux/platform_device.h>
> #include <linux/sched_clock.h>
> #include <linux/smp.h>
> +#include <linux/nmi.h>
>
> /* ARMv8 Cortex-A53 specific event types. */
> #define ARMV8_A53_PERFCTR_PREF_LINEFILL 0xC2
> @@ -1284,10 +1285,16 @@ static struct platform_driver armv8_pmu_driver = {
>
> static int __init armv8_pmu_driver_init(void)
> {
> + int ret;
> +
> if (acpi_disabled)
> - return platform_driver_register(&armv8_pmu_driver);
> + ret = platform_driver_register(&armv8_pmu_driver);
> else
> - return arm_pmu_acpi_probe(armv8_pmuv3_init);
> + ret = arm_pmu_acpi_probe(armv8_pmuv3_init);
> +
> + hld_detector_delay_initialized = true;
> + wake_up(&hld_detector_wait);
> + return ret;
> }
> device_initcall(armv8_pmu_driver_init)
>
> diff --git a/arch/arm64/kernel/watchdog_hld.c b/arch/arm64/kernel/watchdog_hld.c
> new file mode 100644
> index 000000000000..379743e0d001
> --- /dev/null
> +++ b/arch/arm64/kernel/watchdog_hld.c
> @@ -0,0 +1,36 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/nmi.h>
> +#include <linux/cpufreq.h>
> +#include <linux/perf/arm_pmu.h>
> +
> +/*
> + * Safe maximum CPU frequency in case a particular platform doesn't implement
> + * cpufreq driver. Although, architecture doesn't put any restrictions on
> + * maximum frequency but 5 GHz seems to be safe maximum given the available
> + * Arm CPUs in the market which are clocked much less than 5 GHz. On the other
> + * hand, we can't make it much higher as it would lead to a large hard-lockup
> + * detection timeout on parts which are running slower (eg. 1GHz on
> + * Developerbox) and doesn't possess a cpufreq driver.
> + */
> +#define SAFE_MAX_CPU_FREQ 5000000000UL // 5 GHz
> +u64 hw_nmi_get_sample_period(int watchdog_thresh)
> +{
> + unsigned int cpu = smp_processor_id();
> + unsigned long max_cpu_freq;
> +
> + max_cpu_freq = cpufreq_get_hw_max_freq(cpu) * 1000UL;
> + if (!max_cpu_freq)
> + max_cpu_freq = SAFE_MAX_CPU_FREQ;
> +
> + return (u64)max_cpu_freq * watchdog_thresh;
> +}
> +
> +int __init watchdog_nmi_probe(void)
> +{
> + if (!hld_detector_delay_initialized)
> + return -EBUSY;
> + else if (!arm_pmu_irq_is_nmi())
> + return -ENODEV;
> +
> + return hardlockup_detector_perf_init();
> +}
> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index 3cbc3baf087f..2aecb0c34290 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -697,6 +697,11 @@ static int armpmu_get_cpu_irq(struct arm_pmu *pmu, int cpu)
> return per_cpu(hw_events->irq, cpu);
> }
>
> +bool arm_pmu_irq_is_nmi(void)
> +{
> + return has_nmi;
> +}
> +
> /*
> * PMU hardware loses all context when a CPU goes offline.
> * When a CPU is hotplugged back in, since some hardware registers are
> diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
> index 505480217cf1..bf7966776c55 100644
> --- a/include/linux/perf/arm_pmu.h
> +++ b/include/linux/perf/arm_pmu.h
> @@ -163,6 +163,8 @@ int arm_pmu_acpi_probe(armpmu_init_fn init_fn);
> static inline int arm_pmu_acpi_probe(armpmu_init_fn init_fn) { return 0; }
> #endif
>
> +bool arm_pmu_irq_is_nmi(void);
> +
> /* Internal functions only for core arm_pmu code */
> struct arm_pmu *armpmu_alloc(void);
> struct arm_pmu *armpmu_alloc_atomic(void);
> --
> 2.31.1
>
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