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Subject: [PATCH 4/5] resource: Report parent to walk_iomem_res_desc()
 callback
From:   Dan Williams <dan.j.williams@intel.com>
To:     linux-acpi@vger.kernel.org
Cc:     Jason Gunthorpe <jgg@ziepe.ca>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Wei Yang <richardw.yang@linux.intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>, peterz@infradead.org,
        ard.biesheuvel@linaro.org, linux-nvdimm@lists.01.org,
        linux-kernel@vger.kernel.org
Date:   Mon, 02 Mar 2020 14:20:20 -0800
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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@ziepe.ca>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 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);