properly lock nmi enable; delete comment about not locking nmi enable.

Reference: /n/atom/patch/applied/nmilock
Date: Tue Jan  7 17:39:00 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/k10/fns.h	Tue Jan  7 17:38:31 2014
+++ /sys/src/nix/k10/fns.h	Tue Jan  7 17:38:31 2014
@@ -75,6 +75,7 @@
 uintmem	mmuphysaddr(uintptr);
 int	mmuwalk(PTE*, uintptr, int, PTE**, uintmem (*)(usize));
 void	ndnr(void);
+void	nmienable(void);
 void	noerrorsleft(void);
 uchar	nvramread(int);
 void	nvramwrite(int, uchar);
@@ -103,7 +104,6 @@
 int	vmapsync(uintptr);
 void	vsvminit(int);
 void	vunmap(void*, usize);
-int	ainc8(void*);
 
 u64int	getcr0(void);
 void	putcr0(u64int);
@@ -122,6 +122,7 @@
 void	writeconf(void);
 void	wrmsr(u32int, u64int);
 
+int	ainc8(void*);
 int	cas32(void*, u32int, u32int);
 int	cas64(void*, u64int, u64int);
 int	tas32(void*);
--- /sys/src/nix/k10/devrtc.c	Tue Jan  7 17:38:31 2014
+++ /sys/src/nix/k10/devrtc.c	Tue Jan  7 17:38:31 2014
@@ -458,3 +458,18 @@
 	outb(Pdata, data);
 	iunlock(&nvrtlock);
 }
+
+void
+nmienable(void)
+{
+	int x;
+
+	ilock(&nvrtlock);
+	outb(0x70, 0x80);		/* NMI latch clear */
+	outb(0x70, 0);
+
+	x = inb(0x61) & 0x07;		/* Enable NMI */
+	outb(0x61, 0x08|x);
+	outb(0x61, x);
+	iunlock(&nvrtlock);
+}
--- /sys/src/nix/k10/trap.c	Tue Jan  7 17:38:32 2014
+++ /sys/src/nix/k10/trap.c	Tue Jan  7 17:38:32 2014
@@ -166,22 +166,6 @@
 	return oldn - n;
 }
 
-static void
-nmienable(void)
-{
-	int x;
-
-	/*
-	 * Hack: should be locked with NVRAM access.
-	 */
-	outb(0x70, 0x80);		/* NMI latch clear */
-	outb(0x70, 0);
-
-	x = inb(0x61) & 0x07;		/* Enable NMI */
-	outb(0x61, 0x08|x);
-	outb(0x61, x);
-}
-
 void
 trapinit(void)
 {
@@ -343,14 +327,16 @@
 	}
 	else if(vno >= VectorPIC && vno != VectorSYSCALL){
 		static ulong last;
+		static uvlong count[MACHMAX];
 
 		/* spurious interrupt. */
 		lapiceoi(vno);
 		if(sys->ticks - last > 20*HZ){
 			last = sys->ticks;
-			iprint("cpu%d: spurious interrupt %d, last %d\n",
-				m->machno, vno, m->lastintr);
+			iprint("cpu%d: spurious interrupt %d, last %d %lld\n",
+				m->machno, vno, m->lastintr, count[m->machno]);
 		}
+		count[m->machno]++;
 	//	intrtime(vno);
 		if(user)
 			kexit(ureg);
@@ -376,7 +362,6 @@
 		sched();
 		splhi();
 	}
-
 
 	if(user){
 		if(up && up->procctl || up->nnote)