sparc64: Make special trap return path for TRAP_NMI().

We don't want the rtrap path to try and run softirqs or
anything like that when returning from a PIL==15 NMI.
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/include/asm/ttable.h

@@ -162,7 +162,7 @@
 	mov	level, %o0;				\
 	call	routine;				\
 	 add	%sp, PTREGS_OFF, %o1;			\
-	ba,a,pt	%xcc, rtrap_irq;
+	ba,a,pt	%xcc, rtrap_nmi;
 
 #define TRAP_IVEC TRAP_NOSAVE(do_ivec)
 

arch/sparc64/kernel/rtrap.S

@@ -132,6 +132,18 @@ __handle_signal:
 		ba,pt			%xcc, __handle_signal_continue
 		 andn			%l1, %l4, %l1
 
+		/* When returning from a NMI (%pil==15) interrupt we want to
+		 * avoid running softirqs, doing IRQ tracing, preempting, etc.
+		 */
+		.globl			rtrap_nmi
+rtrap_nmi:	ldx			[%sp + PTREGS_OFF + PT_V9_TSTATE], %l1
+		sethi			%hi(0xf << 20), %l4
+		and			%l1, %l4, %l4
+		andn			%l1, %l4, %l1
+		srl			%l4, 20, %l4
+		ba,pt			%xcc, rtrap_no_irq_enable
+		 wrpr			%l4, %pil
+
 		.align			64
 		.globl			rtrap_irq, rtrap, irqsz_patchme, rtrap_xcall
 rtrap_irq:
@@ -161,8 +173,8 @@ rtrap_xcall:
 		call			trace_hardirqs_on
 		 nop
 		wrpr			%l4, %pil
-rtrap_no_irq_enable:
 #endif
+rtrap_no_irq_enable:
 		andcc			%l1, TSTATE_PRIV, %l3
 		bne,pn			%icc, to_kernel
 		 nop