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 <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Chen-Yu Tsai <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: Colin Cross <[email protected]>
Cc: Daniel Thompson <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Lecopzer Chen <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Masayoshi Mizuma <[email protected]>
Cc: Matthias Kaehlcke <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Pingfan Liu <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: "Ravi V. Shankar" <[email protected]>
Cc: Ricardo Neri <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Stephen Boyd <[email protected]>
Cc: Sumit Garg <[email protected]>
Cc: Tzung-Bi Shih <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

2 files changed, 12 insertions, 1 deletions

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");