From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Ross Zwisler <zwisler@xxxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: linux-nvdimm@xxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
---
b/kernel/resource.c | 10 ++++++++++
b/mm/memory_hotplug.c | 5 -----
2 files changed, 10 insertions(+), 5 deletions(-)
diff -puN kernel/resource.c~move-request_region-check kernel/resource.c
--- a/kernel/resource.c~move-request_region-check 2019-01-24 15:13:14.453199539 -0800
+++ b/kernel/resource.c 2019-01-24 15:13:14.458199539 -0800
@@ -1123,6 +1123,16 @@ struct resource * __request_region(struc
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. Be verbose if one is encountered.
+ */
+ if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) {
+ pr_debug("Resource conflict with unaddressable "
+ "device memory at %#010llx !\n",
+ (unsigned long long)start);
+ }
if (conflict != parent) {
if (!(conflict->flags & IORESOURCE_BUSY)) {
parent = conflict;
diff -puN mm/memory_hotplug.c~move-request_region-check mm/memory_hotplug.c
--- a/mm/memory_hotplug.c~move-request_region-check 2019-01-24 15:13:14.455199539 -0800
+++ b/mm/memory_hotplug.c 2019-01-24 15:13:14.459199539 -0800
@@ -109,11 +109,6 @@ static struct resource *register_memory_
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);
_
