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 <[email protected]>
Reviewed-by: Jerome Glisse <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Vishal Verma <[email protected]>
Cc: Tom Lendacky <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Huang Ying <[email protected]>
Cc: Fengguang Wu <[email protected]>
Cc: Keith Busch <[email protected]>
Signed-off-by: Dan Williams <[email protected]>

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)
 			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;
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)
 	res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 	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);
 		kfree(res);
 		return ERR_PTR(-EEXIST);