From: Vishal Verma <vishal.l.verma@xxxxxxxxx>
With DAX memory regions originating from CXL memory expanders or
NVDIMMs, the kmem driver may be hot-adding huge amounts of system memory
on a system without enough 'regular' main memory to support the memmap
for it. To avoid this, ensure that all kmem managed hotplugged memory is
added with the MHP_MEMMAP_ON_MEMORY flag to place the memmap on the
new memory region being hot added.
To do this, call add_memory() in chunks of memory_block_size_bytes() as
that is a requirement for memmap_on_memory.
Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
drivers/dax/kmem.c | 81 +++++++++++++++++++++++++++++++++-------------
1 file changed, 59 insertions(+), 22 deletions(-)
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 898ca9505754..840bf7b40a44 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -12,6 +12,7 @@
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/memory-tiers.h>
+#include <linux/memory_hotplug.h>
#include "dax-private.h"
#include "bus.h"
@@ -105,6 +106,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
data->mgid = rc;
for (i = 0; i < dev_dax->nr_range; i++) {
+ u64 cur_start, cur_len, remaining;
struct resource *res;
struct range range;
@@ -137,21 +139,42 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
res->flags = IORESOURCE_SYSTEM_RAM;
/*
- * Ensure that future kexec'd kernels will not treat
- * this as RAM automatically.
+ * Add memory in chunks of memory_block_size_bytes() so that
+ * it is considered for MHP_MEMMAP_ON_MEMORY
+ * @range has already been aligned to memory_block_size_bytes(),
+ * so the following loop will always break it down cleanly.
*/
- rc = add_memory_driver_managed(data->mgid, range.start,
- range_len(&range), kmem_name, MHP_NID_IS_MGID);
-
- if (rc) {
- dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
- i, range.start, range.end);
- remove_resource(res);
- kfree(res);
- data->res[i] = NULL;
- if (mapped)
- continue;
- goto err_request_mem;
+ cur_start = range.start;
+ cur_len = memory_block_size_bytes();
+ remaining = range_len(&range);
+ while (remaining) {
+ /*
+ * If alignment rules are not satisified we will
+ * fallback normal memmap allocation.
+ */
+ mhp_t mhp_flags = MHP_NID_IS_MGID | MHP_MEMMAP_ON_MEMORY;
+ /*
+ * Ensure that future kexec'd kernels will not treat
+ * this as RAM automatically.
+ */
+ rc = add_memory_driver_managed(data->mgid, cur_start,
+ cur_len, kmem_name,
+ mhp_flags);
+
+ if (rc) {
+ dev_warn(dev,
+ "mapping%d: %#llx-%#llx memory add failed\n",
+ i, cur_start, cur_start + cur_len - 1);
+ remove_resource(res);
+ kfree(res);
+ data->res[i] = NULL;
+ if (mapped)
+ continue;
+ goto err_request_mem;
+ }
+
+ cur_start += cur_len;
+ remaining -= cur_len;
}
mapped++;
}
@@ -186,25 +209,39 @@ static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
* unbind will succeed even if we return failure.
*/
for (i = 0; i < dev_dax->nr_range; i++) {
+
+ u64 cur_start, cur_len, remaining;
struct range range;
+ bool resource_remove;
int rc;
rc = dax_kmem_range(dev_dax, i, &range);
if (rc)
continue;
- rc = remove_memory(range.start, range_len(&range));
- if (rc == 0) {
+ resource_remove = true;
+ cur_start = range.start;
+ cur_len = memory_block_size_bytes();
+ remaining = range_len(&range);
+ while (remaining) {
+
+ rc = remove_memory(cur_start, cur_len);
+ if (rc) {
+ resource_remove = false;
+ dev_err(dev,
+ "mapping%d: %#llx-%#llx cannot be hotremoved until the next reboot\n",
+ i, cur_start, cur_len);
+ }
+ cur_start += cur_len;
+ remaining -= cur_len;
+ }
+ if (resource_remove) {
remove_resource(data->res[i]);
kfree(data->res[i]);
data->res[i] = NULL;
success++;
- continue;
- }
- any_hotremove_failed = true;
- dev_err(dev,
- "mapping%d: %#llx-%#llx cannot be hotremoved until the next reboot\n",
- i, range.start, range.end);
+ } else
+ any_hotremove_failed = true;
}
if (success >= dev_dax->nr_range) {
--
2.41.0
