diff options
authorDave Hansen <>2019-02-25 10:57:33 -0800
committerDan Williams <>2019-02-28 10:41:23 -0800
commitb926b7f3baecb2a855db629e6822e1a85212e91c (patch)
parent5cd401ace914dc68556c6d2fcae0c349444d5f86 (diff)
mm/resource: Move HMM pr_debug() deeper into resource code
HMM consumes physical address space for its own use, even though nothing is mapped or accessible there. It uses a special resource description (IORES_DESC_DEVICE_PRIVATE_MEMORY) to uniquely identify these areas. When HMM consumes address space, it makes a best guess about what to consume. However, it is possible that a future memory or device hotplug can collide with the reserved area. In the case of these conflicts, there is an error message in register_memory_resource(). Later patches in this series move register_memory_resource() from using request_resource_conflict() to __request_region(). Unfortunately, __request_region() does not return the conflict like the previous function did, which makes it impossible to check for IORES_DESC_DEVICE_PRIVATE_MEMORY in a conflicting resource. Instead of warning in register_memory_resource(), move the check into the core resource code itself (__request_region()) where the conflicting resource _is_ available. This has the added bonus of producing a warning in case of HMM conflicts with devices *or* RAM address space, as opposed to the RAM- only warnings that were there previously. Signed-off-by: Dave Hansen <> Reviewed-by: Jerome Glisse <> Cc: Dan Williams <> Cc: Dave Jiang <> Cc: Ross Zwisler <> Cc: Vishal Verma <> Cc: Tom Lendacky <> Cc: Andrew Morton <> Cc: Michal Hocko <> Cc: Cc: Cc: Cc: Huang Ying <> Cc: Fengguang Wu <> Cc: Keith Busch <> Signed-off-by: Dan Williams <>
2 files changed, 9 insertions, 5 deletions
diff --git a/kernel/resource.c b/kernel/resource.c
index ca7ed5158cff..35fe105d581e 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1132,6 +1132,15 @@ struct resource * __request_region(struct resource *parent,
conflict = __request_resource(parent, res);
if (!conflict)
+ /*
+ * 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;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b9a667d36c55..e198974c968d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -110,11 +110,6 @@ static struct resource *register_memory_resource(u64 start, u64 size)
conflict = request_resource_conflict(&iomem_resource, res);
if (conflict) {
- if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) {
- pr_debug("Device unaddressable memory block "
- "memory hotplug at %#010llx !\n",
- (unsigned long long)start);
- }
pr_debug("System RAM resource %pR cannot be added\n", res);
return ERR_PTR(-EEXIST);