From: Ingo Molnar <mingo@elte.hu>
Date: Wed, 17 Oct 2007 16:04:34 +0000 (+0200)
Subject: x86: enable NMI watchdog on nosmp
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=3fb450a327fc098efe6c9f000d470abac354cfcc;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git

x86: enable NMI watchdog on nosmp

if nosmp has been passed as a boot option, but nmi_watchdog=2 has also
been enabled then keep minimal local APIC functionality around to make
the watchdog work.

this allowed me to debug a hard hang that would only occur with a nosmp
bootup.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---

diff --git a/arch/x86/kernel/smpboot_32.c b/arch/x86/kernel/smpboot_32.c
index edc9db69a118..83e4f40f8dc9 100644
--- a/arch/x86/kernel/smpboot_32.c
+++ b/arch/x86/kernel/smpboot_32.c
@@ -1021,6 +1021,12 @@ static void __init smp_boot_cpus(unsigned int max_cpus)
 	if (!max_cpus) {
 		smp_found_config = 0;
 		printk(KERN_INFO "SMP mode deactivated, forcing use of dummy APIC emulation.\n");
+
+		if (nmi_watchdog == NMI_LOCAL_APIC) {
+			printk(KERN_INFO "activating minimal APIC for NMI watchdog use.\n");
+			connect_bsp_APIC();
+			setup_local_APIC();
+		}
 		smpboot_clear_io_apic_irqs();
 		phys_cpu_present_map = physid_mask_of_physid(0);
 		cpu_set(0, per_cpu(cpu_sibling_map, 0));