diff options
authorDave Hansen <>2019-02-25 10:57:36 -0800
committerDan Williams <>2019-02-28 10:41:23 -0800
commit2794129e902d8eb69413d884dc6404b8716ed9ed (patch)
parentb926b7f3baecb2a855db629e6822e1a85212e91c (diff)
mm/memory-hotplug: Allow memory resources to be children
The mm/resource.c code is used to manage the physical address space. The current resource configuration can be viewed in /proc/iomem. An example of this is at the bottom of this description. The nvdimm subsystem "owns" the physical address resources which map to persistent memory and has resources inserted for them as "Persistent Memory". The best way to repurpose this for volatile use is to leave the existing resource in place, but add a "System RAM" resource underneath it. This clearly communicates the ownership relationship of this memory. The request_resource_conflict() API only deals with the top-level resources. Replace it with __request_region() which will search for !IORESOURCE_BUSY areas lower in the resource tree than the top level. We *could* also simply truncate the existing top-level "Persistent Memory" resource and take over the released address space. But, this means that if we ever decide to hot-unplug the "RAM" and give it back, we need to recreate the original setup, which may mean going back to the BIOS tables. This should have no real effect on the existing collision detection because the areas that truly conflict should be marked IORESOURCE_BUSY. 00000000-00000fff : Reserved 00001000-0009fbff : System RAM 0009fc00-0009ffff : Reserved 000a0000-000bffff : PCI Bus 0000:00 000c0000-000c97ff : Video ROM 000c9800-000ca5ff : Adapter ROM 000f0000-000fffff : Reserved 000f0000-000fffff : System ROM 00100000-9fffffff : System RAM 01000000-01e071d0 : Kernel code 01e071d1-027dfdff : Kernel data 02dc6000-0305dfff : Kernel bss a0000000-afffffff : Persistent Memory (legacy) a0000000-a7ffffff : System RAM b0000000-bffdffff : System RAM bffe0000-bfffffff : Reserved c0000000-febfffff : PCI Bus 0000:00 Signed-off-by: Dave Hansen <> Reviewed-by: Dan Williams <> Reviewed-by: Vishal Verma <> 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: Borislav Petkov <> Cc: Bjorn Helgaas <> Cc: Yaowei Bai <> Cc: Takashi Iwai <> Cc: Jerome Glisse <> Cc: Keith Busch <> Signed-off-by: Dan Williams <>
1 files changed, 15 insertions, 13 deletions
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index e198974c968d..b37f3a5c4833 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -99,19 +99,21 @@ void mem_hotplug_done(void)
/* add this memory to iomem resource */
static struct resource *register_memory_resource(u64 start, u64 size)
- struct resource *res, *conflict;
- res = kzalloc(sizeof(struct resource), GFP_KERNEL);
- if (!res)
- return ERR_PTR(-ENOMEM);
- res->name = "System RAM";
- res->start = start;
- res->end = start + size - 1;
- conflict = request_resource_conflict(&iomem_resource, res);
- if (conflict) {
- pr_debug("System RAM resource %pR cannot be added\n", res);
- kfree(res);
+ struct resource *res;
+ char *resource_name = "System RAM";
+ /*
+ * Request ownership of the new memory range. This might be
+ * a child of an existing resource that was present but
+ * not marked as busy.
+ */
+ res = __request_region(&iomem_resource, start, size,
+ resource_name, flags);
+ if (!res) {
+ pr_debug("Unable to reserve System RAM region: %016llx->%016llx\n",
+ start, start + size);
return ERR_PTR(-EEXIST);
return res;