---

yaml
---
r: 283543
b: refs/heads/master
c: 99e8b9c
h: refs/heads/master
i:
  283541: 0281c82
  283539: 9e568a6
  283535: 350a571
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3603a2512f9e69dc87914ba922eb4a0812b21cd6
+refs/heads/master: 99e8b9ca90d688c3ac7d3a141b701c9694a93925

trunk/arch/x86/Kconfig.debug

@@ -287,4 +287,16 @@ config DEBUG_STRICT_USER_COPY_CHECKS
 
 	  If unsure, or if you run an older (pre 4.4) gcc, say N.
 
+config DEBUG_NMI_SELFTEST
+	bool "NMI Selftest"
+	depends on DEBUG_KERNEL
+	---help---
+	  Enabling this option turns on a quick NMI selftest to verify
+	  that the NMI behaves correctly.
+
+	  This might help diagnose strange hangs that rely on NMI to
+	  function properly.
+
+	  If unsure, say N.
+
 endmenu

trunk/arch/x86/include/asm/smp.h

@@ -225,5 +225,11 @@ extern int hard_smp_processor_id(void);
 
 #endif /* CONFIG_X86_LOCAL_APIC */
 
+#ifdef CONFIG_DEBUG_NMI_SELFTEST
+extern void nmi_selftest(void);
+#else
+#define nmi_selftest() do { } while (0)
+#endif
+
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_X86_SMP_H */

trunk/arch/x86/kernel/Makefile

@@ -80,6 +80,7 @@ obj-$(CONFIG_APB_TIMER)		+= apb_timer.o
 obj-$(CONFIG_AMD_NB)		+= amd_nb.o
 obj-$(CONFIG_DEBUG_RODATA_TEST)	+= test_rodata.o
 obj-$(CONFIG_DEBUG_NX_TEST)	+= test_nx.o
+obj-$(CONFIG_DEBUG_NMI_SELFTEST) += nmi_selftest.o
 
 obj-$(CONFIG_KVM_GUEST)		+= kvm.o
 obj-$(CONFIG_KVM_CLOCK)		+= kvmclock.o

trunk/arch/x86/kernel/nmi_selftest.c

@@ -0,0 +1,179 @@
+/*
+ * arch/x86/kernel/nmi-selftest.c
+ *
+ * Testsuite for NMI: IPIs
+ *
+ * Started by Don Zickus:
+ * (using lib/locking-selftest.c as a guide)
+ *
+ *   Copyright (C) 2011 Red Hat, Inc., Don Zickus <dzickus@redhat.com>
+ */
+
+#include <linux/smp.h>
+#include <linux/cpumask.h>
+#include <linux/delay.h>
+
+#include <asm/apic.h>
+#include <asm/nmi.h>
+
+#define SUCCESS		0
+#define FAILURE		1
+#define TIMEOUT		2
+
+static int nmi_fail;
+
+/* check to see if NMI IPIs work on this machine */
+static DECLARE_BITMAP(nmi_ipi_mask, NR_CPUS) __read_mostly;
+
+static int testcase_total;
+static int testcase_successes;
+static int expected_testcase_failures;
+static int unexpected_testcase_failures;
+static int unexpected_testcase_unknowns;
+
+static int nmi_unk_cb(unsigned int val, struct pt_regs *regs)
+{
+	unexpected_testcase_unknowns++;
+	return NMI_HANDLED;
+}
+
+static void init_nmi_testsuite(void)
+{
+	/* trap all the unknown NMIs we may generate */
+	register_nmi_handler(NMI_UNKNOWN, nmi_unk_cb, 0, "nmi_selftest_unk");
+}
+
+static void cleanup_nmi_testsuite(void)
+{
+	unregister_nmi_handler(NMI_UNKNOWN, "nmi_selftest_unk");
+}
+
+static int test_nmi_ipi_callback(unsigned int val, struct pt_regs *regs)
+{
+        int cpu = raw_smp_processor_id();
+
+        if (cpumask_test_and_clear_cpu(cpu, to_cpumask(nmi_ipi_mask)))
+                return NMI_HANDLED;
+
+        return NMI_DONE;
+}
+
+static void test_nmi_ipi(struct cpumask *mask)
+{
+	unsigned long timeout;
+
+	if (register_nmi_handler(NMI_LOCAL, test_nmi_ipi_callback,
+				 NMI_FLAG_FIRST, "nmi_selftest")) {
+		nmi_fail = FAILURE;
+		return;
+	}
+
+	/* sync above data before sending NMI */
+	wmb();
+
+	apic->send_IPI_mask(mask, NMI_VECTOR);
+
+	/* Don't wait longer than a second */
+	timeout = USEC_PER_SEC;
+	while (!cpumask_empty(mask) && timeout--)
+	        udelay(1);
+
+	/* What happens if we timeout, do we still unregister?? */
+	unregister_nmi_handler(NMI_LOCAL, "nmi_selftest");
+
+	if (!timeout)
+		nmi_fail = TIMEOUT;
+	return;
+}
+
+static void remote_ipi(void)
+{
+	cpumask_copy(to_cpumask(nmi_ipi_mask), cpu_online_mask);
+	cpumask_clear_cpu(smp_processor_id(), to_cpumask(nmi_ipi_mask));
+	test_nmi_ipi(to_cpumask(nmi_ipi_mask));
+}
+
+static void local_ipi(void)
+{
+	cpumask_clear(to_cpumask(nmi_ipi_mask));
+	cpumask_set_cpu(smp_processor_id(), to_cpumask(nmi_ipi_mask));
+	test_nmi_ipi(to_cpumask(nmi_ipi_mask));
+}
+
+static void reset_nmi(void)
+{
+	nmi_fail = 0;
+}
+
+static void dotest(void (*testcase_fn)(void), int expected)
+{
+	testcase_fn();
+	/*
+	 * Filter out expected failures:
+	 */
+	if (nmi_fail != expected) {
+		unexpected_testcase_failures++;
+
+		if (nmi_fail == FAILURE)
+			printk("FAILED |");
+		else if (nmi_fail == TIMEOUT)
+			printk("TIMEOUT|");
+		else
+			printk("ERROR  |");
+		dump_stack();
+	} else {
+		testcase_successes++;
+		printk("  ok  |");
+	}
+	testcase_total++;
+
+	reset_nmi();
+}
+
+static inline void print_testname(const char *testname)
+{
+	printk("%12s:", testname);
+}
+
+void nmi_selftest(void)
+{
+	init_nmi_testsuite();
+
+        /*
+	 * Run the testsuite:
+	 */
+	printk("----------------\n");
+	printk("| NMI testsuite:\n");
+	printk("--------------------\n");
+
+	print_testname("remote IPI");
+	dotest(remote_ipi, SUCCESS);
+	printk("\n");
+	print_testname("local IPI");
+	dotest(local_ipi, SUCCESS);
+	printk("\n");
+
+	cleanup_nmi_testsuite();
+
+	if (unexpected_testcase_failures) {
+		printk("--------------------\n");
+		printk("BUG: %3d unexpected failures (out of %3d) - debugging disabled! |\n",
+			unexpected_testcase_failures, testcase_total);
+		printk("-----------------------------------------------------------------\n");
+	} else if (expected_testcase_failures && testcase_successes) {
+		printk("--------------------\n");
+		printk("%3d out of %3d testcases failed, as expected. |\n",
+			expected_testcase_failures, testcase_total);
+		printk("----------------------------------------------------\n");
+	} else if (expected_testcase_failures && !testcase_successes) {
+		printk("--------------------\n");
+		printk("All %3d testcases failed, as expected. |\n",
+			expected_testcase_failures);
+		printk("----------------------------------------\n");
+	} else {
+		printk("--------------------\n");
+		printk("Good, all %3d testcases passed! |\n",
+			testcase_successes);
+		printk("---------------------------------\n");
+	}
+}

trunk/arch/x86/kernel/smpboot.c

@@ -1142,6 +1142,7 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
 {
 	pr_debug("Boot done.\n");
 
+	nmi_selftest();
 	impress_friends();
 #ifdef CONFIG_X86_IO_APIC
 	setup_ioapic_dest();