[SPARC64]: Provide mmu statistics via sysfs.

If the system supports hypervisor based statistics, allow them to
be fetched, enabled, and disabled via sysfs.

Enable and disable via the boolean:

/sys/devices/systems/cpu/cpuN/mmustat_enable

Statistic values are provided under:

/sys/devices/systems/cpu/cpuN/mmu_status/

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc64/kernel/entry.S b/arch/sparc64/kernel/entry.S
index 5b28315..7d1a118 100644
--- a/arch/sparc64/kernel/entry.S
+++ b/arch/sparc64/kernel/entry.S
@@ -2570,3 +2570,25 @@
 	retl
 	 nop
 	.size	sun4v_svc_clrstatus, .-sun4v_svc_clrstatus
+
+	.globl	sun4v_mmustat_conf
+	.type	sun4v_mmustat_conf,#function
+sun4v_mmustat_conf:
+	mov	%o1, %o4
+	mov	HV_FAST_MMUSTAT_CONF, %o5
+	ta	HV_FAST_TRAP
+	stx	%o1, [%o4]
+	retl
+	 nop
+	.size	sun4v_mmustat_conf, .-sun4v_mmustat_conf
+
+	.globl	sun4v_mmustat_info
+	.type	sun4v_mmustat_info,#function
+sun4v_mmustat_info:
+	mov	%o0, %o4
+	mov	HV_FAST_MMUSTAT_INFO, %o5
+	ta	HV_FAST_TRAP
+	stx	%o1, [%o4]
+	retl
+	 nop
+	.size	sun4v_mmustat_info, .-sun4v_mmustat_info