powerpc: Add wrappers to enable/disable relocation on exceptions

These wrappers hide the parameters that have to be passed to H_SET_MODE
to enable/disable relocation on during exceptions.

As noted in the comments, since these have partition wide scope, they
may take some time to complete and must be periodically retried until
H_SUCCESS is returned.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/plpar_wrappers.h

@@ -279,4 +279,29 @@ static inline long plpar_set_mode(unsigned long mflags, unsigned long resource,
 {
 	return plpar_hcall_norets(H_SET_MODE, mflags, resource, value1, value2);
 }
+
+/*
+ * Enable relocation on exceptions on this partition
+ *
+ * Note: this call has a partition wide scope and can take a while to complete.
+ * If it returns H_LONG_BUSY_* it should be retried periodically until it
+ * returns H_SUCCESS.
+ */
+static inline long enable_reloc_on_exceptions(void)
+{
+	/* mflags = 3: Exceptions at 0xC000000000004000 */
+	return plpar_set_mode(3, 3, 0, 0);
+}
+
+/*
+ * Disable relocation on exceptions on this partition
+ *
+ * Note: this call has a partition wide scope and can take a while to complete.
+ * If it returns H_LONG_BUSY_* it should be retried periodically until it
+ * returns H_SUCCESS.
+ */
+static inline long disable_reloc_on_exceptions(void) {
+	return plpar_set_mode(0, 3, 0, 0);
+}
+
 #endif /* _PSERIES_PLPAR_WRAPPERS_H */