1 files changed, 15 insertions, 3 deletions

diff --git a/kernel/resource.c b/kernel/resource.c
index e81b17b53fa5..92190f62ebc5 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -382,7 +382,7 @@ static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
                                  int (*func)(struct resource *, void *))
 {
         struct resource res;
-        int ret = -1;
+        int ret = -EINVAL;
 
         while (start < end &&
                !find_next_iomem_res(start, end, flags, desc, first_lvl, &res)) {
@@ -452,6 +452,9 @@ int walk_mem_res(u64 start, u64 end, void *arg,
  * This function calls the @func callback against all memory ranges of type
  * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
  * It is to be used only for System RAM.
+ *
+ * This will find System RAM ranges that are children of top-level resources
+ * in addition to top-level System RAM resources.
  */
 int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
                           void *arg, int (*func)(unsigned long, unsigned long, void *))
@@ -460,14 +463,14 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
         unsigned long flags;
         struct resource res;
         unsigned long pfn, end_pfn;
-        int ret = -1;
+        int ret = -EINVAL;
 
         start = (u64) start_pfn << PAGE_SHIFT;
         end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1;
         flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
         while (start < end &&
                !find_next_iomem_res(start, end, flags, IORES_DESC_NONE,
-                                    true, &res)) {
+                                    false, &res)) {
                 pfn = (res.start + PAGE_SIZE - 1) >> PAGE_SHIFT;
                 end_pfn = (res.end + 1) >> PAGE_SHIFT;
                 if (end_pfn > pfn)
@@ -1128,6 +1131,15 @@ struct resource * __request_region(struct resource *parent,
                 conflict = __request_resource(parent, res);
                 if (!conflict)
                         break;
+                /*
+                 * mm/hmm.c reserves physical addresses which then
+                 * become unavailable to other users.  Conflicts are
+                 * not expected.  Warn to aid debugging if encountered.
+                 */
+                if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) {
+                        pr_warn("Unaddressable device %s %pR conflicts with %pR",
+                                conflict->name, conflict, res);
+                }
                 if (conflict != parent) {
                         if (!(conflict->flags & IORESOURCE_BUSY)) {
                                 parent = conflict;