[PATCH] x86: Allow users to force a panic on NMI

To quote Alan Cox:

The default Linux behaviour on an NMI of either memory or unknown is to
continue operation. For many environments such as scientific computing
it is preferable that the box is taken out and the error dealt with than
an uncorrected parity/ECC error get propogated.

A small number of systems do generate NMI's for bizarre random reasons
such as power management so the default is unchanged. In other respects
the new proc/sys entry works like the existing panic controls already in
that directory.

This is separate to the edac support - EDAC allows supported chipsets to
handle ECC errors well, this change allows unsupported cases to at least
panic rather than cause problems further down the line.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andi Kleen <ak@suse.de>

6 files changed, 23 insertions, 0 deletions

diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 7db664d0b25c..2f6cb8276480 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -635,6 +635,8 @@ static void mem_parity_error(unsigned char reason, struct pt_regs * regs)
                         "to continue\n");
         printk(KERN_EMERG "You probably have a hardware problem with your RAM "
                         "chips\n");
+        if (panic_on_unrecovered_nmi)
+                panic("NMI: Not continuing");
 
         /* Clear and disable the memory parity error line. */
         clear_mem_error(reason);
@@ -670,6 +672,10 @@ static void unknown_nmi_error(unsigned char reason, struct pt_regs * regs)
                 reason, smp_processor_id());
         printk("Dazed and confused, but trying to continue\n");
         printk("Do you have a strange power saving mode enabled?\n");
+
+        if (panic_on_unrecovered_nmi)
+                panic("NMI: Not continuing");
+
 }
 
 static DEFINE_SPINLOCK(nmi_print_lock);
diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 42bc070fdf11..b18829db2a6a 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -732,6 +732,8 @@ mem_parity_error(unsigned char reason, struct pt_regs * regs)
 {
         printk("Uhhuh. NMI received. Dazed and confused, but trying to continue\n");
         printk("You probably have a hardware problem with your RAM chips\n");
+        if (panic_on_unrecovered_nmi)
+               panic("NMI: Not continuing");
 
         /* Clear and disable the memory parity error line. */
         reason = (reason & 0xf) | 4;
@@ -757,6 +759,10 @@ unknown_nmi_error(unsigned char reason, struct pt_regs * regs)
 {       printk("Uhhuh. NMI received for unknown reason %02x.\n", reason);
         printk("Dazed and confused, but trying to continue\n");
         printk("Do you have a strange power saving mode enabled?\n");
+
+        if (panic_on_unrecovered_nmi)
+                panic("NMI: Not continuing");
+
 }
 
 /* Runs on IST stack. This code must keep interrupts off all the time.
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2b2ae4fdce8b..1ff9609300b4 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -186,6 +186,7 @@ extern void bust_spinlocks(int yes);
 extern int oops_in_progress;            /* If set, an oops, panic(), BUG() or die() is in progress */
 extern int panic_timeout;
 extern int panic_on_oops;
+extern int panic_on_unrecovered_nmi;
 extern int tainted;
 extern const char *print_tainted(void);
 extern void add_taint(unsigned);
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index ecb79ba52ae1..432778446ad2 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -151,6 +151,7 @@ enum
         KERN_COMPAT_LOG=73,     /* int: print compat layer  messages */
         KERN_MAX_LOCK_DEPTH=74,
         KERN_NMI_WATCHDOG=75, /* int: enable/disable nmi watchdog */
+        KERN_PANIC_ON_NMI=76, /* int: whether we will panic on an unrecovered */
 };
 
 
diff --git a/kernel/panic.c b/kernel/panic.c
index 8010b9b17aca..d2db3e2209e0 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -21,6 +21,7 @@
 #include <linux/debug_locks.h>
 
 int panic_on_oops;
+int panic_on_unrecovered_nmi;
 int tainted;
 static int pause_on_oops;
 static int pause_on_oops_flag;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 040de6bd74dd..220e20564124 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -642,6 +642,14 @@ static ctl_table kern_table[] = {
 #endif
 #if defined(CONFIG_X86)
         {
+                .ctl_name       = KERN_PANIC_ON_NMI,
+                .procname       = "panic_on_unrecovered_nmi",
+                .data           = &panic_on_unrecovered_nmi,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec,
+        },
+        {
                 .ctl_name       = KERN_BOOTLOADER_TYPE,
                 .procname       = "bootloader_type",
                 .data           = &bootloader_type,