From b17aa959330e8058452297049a0056ba4b9c72e8 Mon Sep 17 00:00:00 2001
From: Douglas Anderson <dianders@chromium.org>
Date: Fri, 19 May 2023 10:18:39 -0700
Subject: [PATCH] watchdog/perf: add a weak function for an arch to detect if
 perf can use NMIs

On arm64, NMI support needs to be detected at runtime.  Add a weak
function to the perf hardlockup detector so that an architecture can
implement it to detect whether NMIs are available.

Link: https://lkml.kernel.org/r/20230519101840.v5.15.Ic55cb6f90ef5967d8aaa2b503a4e67c753f64d3a@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/nmi.h    |  1 +
 kernel/watchdog_perf.c | 12 +++++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 1cdadc6a6cfd..28e65fd1de13 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -208,6 +208,7 @@ static inline bool trigger_single_cpu_backtrace(int cpu)
 
 #ifdef CONFIG_HARDLOCKUP_DETECTOR_PERF
 u64 hw_nmi_get_sample_period(int watchdog_thresh);
+bool arch_perf_nmi_is_available(void);
 #endif
 
 #if defined(CONFIG_HARDLOCKUP_CHECK_TIMESTAMP) && \
diff --git a/kernel/watchdog_perf.c b/kernel/watchdog_perf.c
index 349fcd4d2abc..8ea00c4a24b2 100644
--- a/kernel/watchdog_perf.c
+++ b/kernel/watchdog_perf.c
@@ -234,12 +234,22 @@ void __init hardlockup_detector_perf_restart(void)
 	}
 }
 
+bool __weak __init arch_perf_nmi_is_available(void)
+{
+	return true;
+}
+
 /**
  * watchdog_hardlockup_probe - Probe whether NMI event is available at all
  */
 int __init watchdog_hardlockup_probe(void)
 {
-	int ret = hardlockup_detector_event_create();
+	int ret;
+
+	if (!arch_perf_nmi_is_available())
+		return -ENODEV;
+
+	ret = hardlockup_detector_event_create();
 
 	if (ret) {
 		pr_info("Perf NMI watchdog permanently disabled\n");