Use an interrupt gate for the NMI handler and prevent too-early

enabling of interrupts inside of trap().  Fix a typo in a comment.

Revert rev 1.113 of "sys/i386/i386/exception.s" as it is no longer
needed.

Reviewed by:	bde
MFC after:	3 days

3 files changed, 7 insertions, 31 deletions

diff --git a/sys/i386/i386/exception.s b/sys/i386/i386/exception.s
index 6a45179..2e69ab8 100644
--- a/sys/i386/i386/exception.s
+++ b/sys/i386/i386/exception.s
@@ -78,6 +78,8 @@ IDTVEC(div)
 	pushl $0; TRAP(T_DIVIDE)
 IDTVEC(dbg)
 	pushl $0; TRAP(T_TRCTRAP)
+IDTVEC(nmi)
+	pushl $0; TRAP(T_NMI)
 IDTVEC(bpt)
 	pushl $0; TRAP(T_BPTFLT)
 IDTVEC(ofl)
@@ -213,33 +215,6 @@ ENTRY(fork_trampoline)
 	MEXITCOUNT
 	jmp	doreti
 
-/*
- * NMI handling is somewhat special: NMI interrupts may be taken at
- * any time, including when the processor has turned off external
- * interrupts by clearing EFLAGS.IF.  This means that the kernel's
- * internal state could be inconsistent at the time of the interrupt,
- * and it is not safe to call "ast()" as is done in the exit path
- * for normal interrupts.
- *
- * The NMI handler therefore invokes the C language routine "trap()"
- * and directly jumps to 'doreti_exit'.
- */
-IDTVEC(nmi)
-	/* create a trap frame */
-	pushl	$0
-	pushl	$T_NMI
-	pushal
-	pushl	%ds
-	pushl	%es
-	pushl	%fs
-	movl	$KDSEL,%eax
-	movl	%eax,%ds
-	movl	%eax,%es
-	movl	$KPSEL,%eax
-	movl	%eax,%fs
-	FAKE_MCOUNT(TF_EIP(%esp))
-	call	trap
-	jmp	doreti_exit
 
 /*
  * To efficiently implement classification of trap and interrupt handlers
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index be715d0..f413a20 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -2114,7 +2114,7 @@ init386(first)
 	    GSEL(GCODE_SEL, SEL_KPL));
 	setidt(IDT_DB, &IDTVEC(dbg),  SDT_SYS386IGT, SEL_KPL,
 	    GSEL(GCODE_SEL, SEL_KPL));
-	setidt(IDT_NMI, &IDTVEC(nmi),  SDT_SYS386TGT, SEL_KPL,
+	setidt(IDT_NMI, &IDTVEC(nmi),  SDT_SYS386IGT, SEL_KPL,
 	    GSEL(GCODE_SEL, SEL_KPL));
  	setidt(IDT_BP, &IDTVEC(bpt),  SDT_SYS386IGT, SEL_UPL,
 	    GSEL(GCODE_SEL, SEL_KPL));
diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index be714dd..1e5a346 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -238,11 +238,12 @@ trap(frame)
 			printf("kernel trap %d with interrupts disabled\n",
 			    type);
 			/*
-			 * Page faults need interrupts diasabled until later,
+			 * Page faults need interrupts disabled until later,
 			 * and we shouldn't enable interrupts while in a
-			 * critical section.
+			 * critical section or if servicing an NMI.
 			 */
-			if (type != T_PAGEFLT && td->td_critnest == 0)
+			if (type != T_NMI && type != T_PAGEFLT &&
+			    td->td_critnest == 0)
 				enable_intr();
 		}
 	}