s390/mm: allow to check if a gmap shadow is valid

[deliverable/linux.git] / arch / s390 / mm / gmap.c

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 4a1434bc2f0e7b7c8499b8f100792328172ca5c8..d00e4abb559e10b934276a0b36095e2d98536100 100644 (file)
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -1407,6 +1407,26 @@ static struct gmap *gmap_find_shadow(struct gmap *parent, unsigned long asce,
        return NULL;
 }
 
+/**
+ * gmap_shadow_valid - check if a shadow guest address space matches the
+ *                     given properties and is still valid
+ * @sg: pointer to the shadow guest address space structure
+ * @asce: ASCE for which the shadow table is requested
+ * @edat_level: edat level to be used for the shadow translation
+ *
+ * Returns 1 if the gmap shadow is still valid and matches the given
+ * properties, the caller can continue using it. Returns 0 otherwise, the
+ * caller has to request a new shadow gmap in this case.
+ *
+ */
+int gmap_shadow_valid(struct gmap *sg, unsigned long asce, int edat_level)
+{
+       if (sg->removed)
+               return 0;
+       return sg->orig_asce == asce && sg->edat_level == edat_level;
+}
+EXPORT_SYMBOL_GPL(gmap_shadow_valid);
+
 /**
  * gmap_shadow - create/find a shadow guest address space
  * @parent: pointer to the parent gmap