[PATCH] xen/arm: Handle empty grant table region in find_unallocated_memory()

[Michal Orzel <michal.orzel@xxxxxxx>]

When creating dom0 with grant table support disabled in Xen and no IOMMU,
the following assert is triggered (debug build):
"Assertion 's <= e' failed at common/rangeset.c:189"

This is because find_unallocated_memory() (used to find memory holes
for extended regions) calls rangeset_remove_range() for an empty
grant table region. Fix it by checking if the size of region is not 0.

Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
---
 xen/arch/arm/domain_build.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 54bf5623c889..2e899458acdf 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -1633,14 +1633,18 @@ static int __init find_unallocated_memory(const struct 
kernel_info *kinfo,
     }
 
     /* Remove grant table region */
-    start = kinfo->gnttab_start;
-    end = kinfo->gnttab_start + kinfo->gnttab_size;
-    res = rangeset_remove_range(unalloc_mem, PFN_DOWN(start), PFN_DOWN(end - 
1));
-    if ( res )
+    if ( kinfo->gnttab_size )
     {
-        printk(XENLOG_ERR "Failed to remove: %#"PRIpaddr"->%#"PRIpaddr"\n",
-               start, end);
-        goto out;
+        start = kinfo->gnttab_start;
+        end = kinfo->gnttab_start + kinfo->gnttab_size;
+        res = rangeset_remove_range(unalloc_mem, PFN_DOWN(start),
+                                    PFN_DOWN(end - 1));
+        if ( res )
+        {
+            printk(XENLOG_ERR "Failed to remove: %#"PRIpaddr"->%#"PRIpaddr"\n",
+                   start, end);
+            goto out;
+        }
     }
 
     start = 0;
-- 
2.25.1