From 0d0efc07f3df677d7622bb760f8e2920b5e33f42 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@kernel.org>
Date: Sat, 2 Apr 2016 07:01:33 -0700
Subject: [PATCH] x86/head: Move the early NMI fixup into C

C is nicer than asm.

Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/dd068269f8d59fe44e9e43a50d0efd67da65c2b5.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/head_32.S | 7 -------
 arch/x86/kernel/head_64.S | 6 ------
 arch/x86/mm/extable.c     | 5 +++++
 3 files changed, 5 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 0904536cd45c..184291c72c22 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -561,9 +561,6 @@ early_idt_handler_common:
 	 */
 	cld
 
-	cmpl $2,(%esp)		# X86_TRAP_NMI
-	je .Lis_nmi		# Ignore NMI
-
 	cmpl $2,%ss:early_recursion_flag
 	je hlt_loop
 	incl %ss:early_recursion_flag
@@ -642,10 +639,6 @@ early_idt_handler_common:
 hlt_loop:
 	hlt
 	jmp hlt_loop
-
-.Lis_nmi:
-	addl $8,%esp		/* drop vector number and error code */
-	iret
 ENDPROC(early_idt_handler_common)
 
 /* This is the default interrupt "handler" :-) */
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 9e8636d2cedd..230843781dd4 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -351,9 +351,6 @@ early_idt_handler_common:
 	 */
 	cld
 
-	cmpl $2,(%rsp)		# X86_TRAP_NMI
-	je .Lis_nmi		# Ignore NMI
-
 	cmpl $2,early_recursion_flag(%rip)
 	jz  1f
 	incl early_recursion_flag(%rip)
@@ -422,9 +419,6 @@ early_idt_handler_common:
 20:	/* Exception table entry found or page table generated */
 	decl early_recursion_flag(%rip)
 	jmp restore_regs_and_iret
-.Lis_nmi:
-	addq $16,%rsp		# drop vector number and error code
-	INTERRUPT_RETURN
 ENDPROC(early_idt_handler_common)
 
 	__INITDATA
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 1366e067a796..4be041910c2f 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -1,5 +1,6 @@
 #include <linux/module.h>
 #include <asm/uaccess.h>
+#include <asm/traps.h>
 
 typedef bool (*ex_handler_t)(const struct exception_table_entry *,
 			    struct pt_regs *, int);
@@ -89,6 +90,10 @@ int __init early_fixup_exception(struct pt_regs *regs, int trapnr)
 	unsigned long new_ip;
 	ex_handler_t handler;
 
+	/* Ignore early NMIs. */
+	if (trapnr == X86_TRAP_NMI)
+		return 1;
+
 	e = search_exception_tables(regs->ip);
 	if (!e)
 		return 0;
-- 
2.20.1