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 <dave.hansen@linux.intel.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: linux-nvdimm@lists.01.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: Huang Ying <ying.huang@intel.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/kernel/resource.c b/kernel/resource.c
index ca7ed51..35fe105 100644 (file)
--- 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 b9a667d..e198974 100644 (file)
--- 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);