s390/mm/kvm: fix mis-merge in gmap handling

commit 1e133ab296f3 ("s390/mm: split arch/s390/mm/pgtable.c") dropped
some changes from commit a3a92c31bf0b ("KVM: s390: fix mismatch
between user and in-kernel guest limit") - this breaks KVM for some
memory sizes (kvm-s390: failed to commit memory region) like
exactly 2GB.

Cc: Dominik Dingel <dingel@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 69247b4dcc43..cace818d86eb 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -23,7 +23,7 @@
 /**
  * gmap_alloc - allocate a guest address space
  * @mm: pointer to the parent mm_struct
- * @limit: maximum size of the gmap address space
+ * @limit: maximum address of the gmap address space
  *
  * Returns a guest address space structure.
  */
@@ -292,7 +292,7 @@ int gmap_map_segment(struct gmap *gmap, unsigned long from,
         if ((from | to | len) & (PMD_SIZE - 1))
                 return -EINVAL;
         if (len == 0 || from + len < from || to + len < to ||
-            from + len > TASK_MAX_SIZE || to + len > gmap->asce_end)
+            from + len - 1 > TASK_MAX_SIZE || to + len - 1 > gmap->asce_end)
                 return -EINVAL;
 
         flush = 0;