[RFC PATCH v2 14/14] x86/watchdog: Add a shim hardlockup detector

[Ricardo Neri]

The generic hardlockup detector is based on perf. It also provides a set
of weak stubs that CPU architectures can override. Add a shim hardlockup
detector for x86 that selects between perf and hpet implementations.

Specifically, this shim implementation is needed for the HPET-based
hardlockup detector; it can also be used for future implementations.

Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Clemens Ladisch <clemens@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Philippe Ombredanne <pombredanne@xxxxxxxx>
Cc: Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
Cc: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Cc: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Cc: Nayna Jain <nayna@xxxxxxxxxxxxx>
Cc: "Ravi V. Shankar" <ravi.v.shankar@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Suggested-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
---
 arch/x86/Kconfig.debug         |  4 ++
 arch/x86/kernel/Makefile       |  1 +
 arch/x86/kernel/watchdog_hld.c | 78 ++++++++++++++++++++++++++++++++++
 3 files changed, 83 insertions(+)
 create mode 100644 arch/x86/kernel/watchdog_hld.c

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 3a2845a29e8a..5e5f4d2330af 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -169,10 +169,14 @@ config IOMMU_LEAK
 config HAVE_MMIOTRACE_SUPPORT
 	def_bool y
 
+config X86_HARDLOCKUP_DETECTOR
+	bool
+
 config X86_HARDLOCKUP_DETECTOR_HPET
 	bool "Use HPET Timer for Hard Lockup Detection"
 	select SOFTLOCKUP_DETECTOR
 	select HARDLOCKUP_DETECTOR
+	select X86_HARDLOCKUP_DETECTOR
 	depends on HPET_TIMER && HPET && X86_64
 	help
 	  Say y to enable a hardlockup detector that is driven by an High-
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 9d610e8a9224..5372453fe2a7 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -106,6 +106,7 @@ obj-$(CONFIG_VM86)		+= vm86_32.o
 obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
 
 obj-$(CONFIG_HPET_TIMER) 	+= hpet.o
+obj-$(CONFIG_X86_HARDLOCKUP_DETECTOR) += watchdog_hld.o
 obj-$(CONFIG_X86_HARDLOCKUP_DETECTOR_HPET) += watchdog_hld_hpet.o
 obj-$(CONFIG_APB_TIMER)		+= apb_timer.o
 
diff --git a/arch/x86/kernel/watchdog_hld.c b/arch/x86/kernel/watchdog_hld.c
new file mode 100644
index 000000000000..a2f6190dbce0
--- /dev/null
+++ b/arch/x86/kernel/watchdog_hld.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * A shim hardlockup detector. It simply overrides the weak stubs of the
+ * generic implementation.
+ *
+ * Copyright (C) Intel Corporation 2019
+ */
+
+#include <linux/nmi.h>
+#include <asm/hpet.h>
+
+enum x86_hardlockup_detector {
+	X86_HARDLOCKUP_DETECTOR_PERF,
+	X86_HARDLOCKUP_DETECTOR_HPET,
+};
+
+static enum __read_mostly x86_hardlockup_detector detector_type;
+
+int watchdog_nmi_enable(unsigned int cpu)
+{
+	if (detector_type == X86_HARDLOCKUP_DETECTOR_PERF) {
+		hardlockup_detector_perf_enable();
+		return 0;
+	}
+
+	if (detector_type == X86_HARDLOCKUP_DETECTOR_HPET) {
+		hardlockup_detector_hpet_enable();
+		return 0;
+	}
+
+	return -ENODEV;
+}
+
+void watchdog_nmi_disable(unsigned int cpu)
+{
+	if (detector_type == X86_HARDLOCKUP_DETECTOR_PERF) {
+		hardlockup_detector_perf_disable();
+		return;
+	}
+
+	if (detector_type == X86_HARDLOCKUP_DETECTOR_HPET) {
+		hardlockup_detector_hpet_disable();
+		return;
+	}
+}
+
+int __init watchdog_nmi_probe(void)
+{
+	int ret;
+
+	/*
+	 * Try first with the HPET hardlockup detector. It will only
+	 * succeed if selected at build time and the nmi_watchdog
+	 * command-line parameter is configured. This ensure that the
+	 * perf-based detector is used by default, if selected at
+	 * build time.
+	 */
+	ret = hardlockup_detector_hpet_init();
+	if (!ret) {
+		detector_type = X86_HARDLOCKUP_DETECTOR_HPET;
+		return ret;
+	}
+
+	ret = hardlockup_detector_perf_init();
+	if (!ret) {
+		detector_type = X86_HARDLOCKUP_DETECTOR_PERF;
+		return ret;
+	}
+
+	return ret;
+}
+
+void watchdog_nmi_stop(void)
+{
+	/* Only the HPET lockup detector defines a stop function. */
+	if (detector_type == X86_HARDLOCKUP_DETECTOR_HPET)
+		hardlockup_detector_hpet_enable();
+}
-- 
2.17.1