rangeset: introduce rangeset_subtract

Introduce rangeset_subtract() to remove regions in r2 from r1.

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/common/rangeset.c

@@ -397,6 +397,18 @@ int rangeset_merge(struct rangeset *r1, struct rangeset *r2)
     return rangeset_report_ranges(r2, 0, ~0UL, merge, r1);
 }
 
+static int cf_check subtract(unsigned long s, unsigned long e, void *data)
+{
+    struct rangeset *r = data;
+
+    return rangeset_remove_range(r, s, e);
+}
+
+int rangeset_subtract(struct rangeset *r1, struct rangeset *r2)
+{
+    return rangeset_report_ranges(r2, 0, ~0UL, subtract, r1);
+}
+
 int rangeset_add_singleton(
     struct rangeset *r, unsigned long s)
 {

xen/include/xen/rangeset.h

@@ -85,6 +85,9 @@ int rangeset_consume_ranges(struct rangeset *r,
 /* Merge rangeset r2 into rangeset r1. */
 int __must_check rangeset_merge(struct rangeset *r1, struct rangeset *r2);
 
+/* Subtract rangeset r2 from rangeset r1. */
+int __must_check rangeset_subtract(struct rangeset *r1, struct rangeset *r2);
+
 /* Add/remove/query a single number. */
 int __must_check rangeset_add_singleton(
     struct rangeset *r, unsigned long s);