[MIPS] SMTC: Fix crash if # of TC's > # of VPE's after pt_regs irq cleanup.

Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/kernel/entry.S

@@ -83,7 +83,10 @@ FEXPORT(syscall_exit)
 FEXPORT(restore_all)			# restore full frame
 #ifdef CONFIG_MIPS_MT_SMTC
 /* Detect and execute deferred IPI "interrupts" */
+	LONG_L	s0, TI_REGS($28)
+	LONG_S	sp, TI_REGS($28)
 	jal	deferred_smtc_ipi
+	LONG_S	s0, TI_REGS($28)
 /* Re-arm any temporarily masked interrupts not explicitly "acked" */
 	mfc0	v0, CP0_TCSTATUS
 	ori	v1, v0, TCSTATUS_IXMT

arch/mips/kernel/smtc-asm.S

@@ -101,7 +101,9 @@ FEXPORT(__smtc_ipi_vector)
 	lw	t0,PT_PADSLOT5(sp)
 	/* Argument from sender passed in stack pad slot 4 */
 	lw	a0,PT_PADSLOT4(sp)
-	PTR_LA	ra, _ret_from_irq
+	LONG_L	s0, TI_REGS($28)
+	LONG_S	sp, TI_REGS($28)
+	PTR_LA	ra, ret_from_irq
 	jr	t0
 
 /*
@@ -119,7 +121,10 @@ LEAF(self_ipi)
 	subu	t1,sp,PT_SIZE
 	sw	ra,PT_EPC(t1)
 	sw	a0,PT_PADSLOT4(t1)
+	LONG_L	s0, TI_REGS($28)
+	LONG_S	sp, TI_REGS($28)
 	la	t2,ipi_decode
+	LONG_S	s0, TI_REGS($28)
 	sw	t2,PT_PADSLOT5(t1)
 	/* Save pre-disable value of TCStatus */
 	sw	t0,PT_TCSTATUS(t1)