Subject: [PATCH] boot: add early NMI counter

From: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>

We currently ignore early NMIs but it would be nice to be able to
know whether they actually occurred.

This patch adds an early NMI counter and exports it trough
/proc/interrupts with the name of ENM (Early NMI).

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
---

diff -urNp linux-3.3-rc6-orig/arch/x86/include/asm/processor.h linux-3.3-rc6/arch/x86/include/asm/processor.h
--- linux-3.3-rc6-orig/arch/x86/include/asm/processor.h	2012-03-07 15:49:01.826241682 +0900
+++ linux-3.3-rc6/arch/x86/include/asm/processor.h	2012-03-07 18:52:27.668054122 +0900
@@ -402,6 +402,7 @@ DECLARE_PER_CPU(char *, irq_stack_ptr);
 DECLARE_PER_CPU(unsigned int, irq_count);
 extern unsigned long kernel_eflags;
 extern asmlinkage void ignore_sysret(void);
+extern unsigned int early_nmi_count;
 #else	/* X86_64 */
 #ifdef CONFIG_CC_STACKPROTECTOR
 /*
diff -urNp linux-3.3-rc6-orig/arch/x86/kernel/head_64.S linux-3.3-rc6/arch/x86/kernel/head_64.S
--- linux-3.3-rc6-orig/arch/x86/kernel/head_64.S	2012-03-07 18:51:17.583160114 +0900
+++ linux-3.3-rc6/arch/x86/kernel/head_64.S	2012-03-07 18:54:37.205699422 +0900
@@ -327,6 +327,7 @@ early_exception_handler:
 	jmp 1b
 
 early_nmi_handler:
+	incl early_nmi_count(%rip) # exported as ENM in /proc/interrupts
 	iretq
 
 #ifdef CONFIG_EARLY_PRINTK
@@ -340,6 +341,10 @@ early_idt_ripmsg:
 #endif /* CONFIG_EARLY_PRINTK */
 	.previous
 
+	.globl early_nmi_count
+early_nmi_count:
+	.long 0
+
 #define NEXT_PAGE(name) \
 	.balign	PAGE_SIZE; \
 ENTRY(name)
diff -urNp linux-3.3-rc6-orig/arch/x86/kernel/irq.c linux-3.3-rc6/arch/x86/kernel/irq.c
--- linux-3.3-rc6-orig/arch/x86/kernel/irq.c	2012-03-07 15:49:01.838241839 +0900
+++ linux-3.3-rc6/arch/x86/kernel/irq.c	2012-03-07 18:55:14.078179448 +0900
@@ -125,6 +125,7 @@ int arch_show_interrupts(struct seq_file
 #if defined(CONFIG_X86_IO_APIC)
 	seq_printf(p, "%*s: %10u\n", prec, "MIS", atomic_read(&irq_mis_count));
 #endif
+	seq_printf(p, "%*s: %10u\n", prec, "ENM", early_nmi_count);
 	return 0;
 }