[PATCH 4/5] resource: Report parent to walk_iomem_res_desc() callback

[Dan Williams]

In support of detecting whether a resource might have been been claimed,
report the parent to the walk_iomem_res_desc() callback. For example,
the ACPI HMAT parser publishes "hmem" platform devices per target range.
However, if the HMAT is disabled / missing a fallback driver can attach
devices to the raw memory ranges as a fallback if it sees unclaimed /
orphan "Soft Reserved" resources in the resource tree.

Otherwise, find_next_iomem_res() returns a resource with garbage data
from the stack allocation in __walk_iomem_res_desc() for the res->parent
field.

Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 kernel/resource.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/resource.c b/kernel/resource.c
index 76036a41143b..6e22e312fd55 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -386,6 +386,7 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
 		res->end = min(end, p->end);
 		res->flags = p->flags;
 		res->desc = p->desc;
+		res->parent = p->parent;
 	}
 
 	read_unlock(&resource_lock);