v4.19.13 snapshot.
diff --git a/arch/x86/kernel/nmi_selftest.c b/arch/x86/kernel/nmi_selftest.c
new file mode 100644
index 0000000..a1a96df
--- /dev/null
+++ b/arch/x86/kernel/nmi_selftest.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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 <linux/init.h>
+#include <linux/percpu.h>
+
+#include <asm/apic.h>
+#include <asm/nmi.h>
+
+#define SUCCESS 0
+#define FAILURE 1
+#define TIMEOUT 2
+
+static int __initdata nmi_fail;
+
+/* check to see if NMI IPIs work on this machine */
+static DECLARE_BITMAP(nmi_ipi_mask, NR_CPUS) __initdata;
+
+static int __initdata testcase_total;
+static int __initdata testcase_successes;
+static int __initdata expected_testcase_failures;
+static int __initdata unexpected_testcase_failures;
+static int __initdata unexpected_testcase_unknowns;
+
+static int __init nmi_unk_cb(unsigned int val, struct pt_regs *regs)
+{
+ unexpected_testcase_unknowns++;
+ return NMI_HANDLED;
+}
+
+static void __init init_nmi_testsuite(void)
+{
+ /* trap all the unknown NMIs we may generate */
+ register_nmi_handler(NMI_UNKNOWN, nmi_unk_cb, 0, "nmi_selftest_unk",
+ __initdata);
+}
+
+static void __init cleanup_nmi_testsuite(void)
+{
+ unregister_nmi_handler(NMI_UNKNOWN, "nmi_selftest_unk");
+}
+
+static int __init 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 __init test_nmi_ipi(struct cpumask *mask)
+{
+ unsigned long timeout;
+
+ if (register_nmi_handler(NMI_LOCAL, test_nmi_ipi_callback,
+ NMI_FLAG_FIRST, "nmi_selftest", __initdata)) {
+ 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 __init remote_ipi(void)
+{
+ cpumask_copy(to_cpumask(nmi_ipi_mask), cpu_online_mask);
+ cpumask_clear_cpu(smp_processor_id(), to_cpumask(nmi_ipi_mask));
+ if (!cpumask_empty(to_cpumask(nmi_ipi_mask)))
+ test_nmi_ipi(to_cpumask(nmi_ipi_mask));
+}
+
+static void __init 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 __init reset_nmi(void)
+{
+ nmi_fail = 0;
+}
+
+static void __init 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(KERN_CONT "FAILED |");
+ else if (nmi_fail == TIMEOUT)
+ printk(KERN_CONT "TIMEOUT|");
+ else
+ printk(KERN_CONT "ERROR |");
+ dump_stack();
+ } else {
+ testcase_successes++;
+ printk(KERN_CONT " ok |");
+ }
+ testcase_total++;
+
+ reset_nmi();
+}
+
+static inline void __init print_testname(const char *testname)
+{
+ printk("%12s:", testname);
+}
+
+void __init 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(KERN_CONT "\n");
+ print_testname("local IPI");
+ dotest(local_ipi, SUCCESS);
+ printk(KERN_CONT "\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");
+ }
+}