[PATCH 03/11] of: reserved_mem: avoid unconditional save of reg entries in fdt_scan_reserved_mem_late()

Chen Wandun
2026-04-29T06:59:14Z

fdt_scan_reserved_mem_late() iterates all reg entries of every
/reserved-memory child and unconditionally initialises each via
fdt_init_reserved_mem_node(), while fdt_scan_reserved_mem() in the
first pass may have rejected individual entries in
early_init_dt_reserve_memory() (e.g. outside physical memory or, on
the no-map path, overlapping an existing reservation).

When a single node mixes failing and succeeding reg entries, the
first-pass counter only accounts for the successful ones, and the
second-pass save then overflows into the wrong slots: the failing
entry may be written to reserved_mem[] while the succeeding one is
dropped by the "not enough space" guard in fdt_init_reserved_mem_node().
The stored entry does not correspond to any real memblock reservation
and misleads consumers such as of_reserved_mem_lookup().

Mirror early_init_dt_reserve_memory()'s preconditions in the
per-reg-entry save loop:

- skip the entry if it does not overlap memblock.memory;
- for nomap entries, skip if the region is already reserved.

This keeps reserved_mem[] strictly consistent with the regions that
were actually reserved.

Fixes: 8a6e02d0c00e ("of: reserved_mem: Restructure how the reserved memory regions are processed")
Signed-off-by: Chen Wandun <chenwandun@lixiang.com>
Tested-by: Zhao Meijing <zhaomeijing@lixiang.com>
---
drivers/of/of_reserved_mem.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 03c676052dab..807b222fce5f 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -288,6 +288,7 @@ void __init fdt_scan_reserved_mem_late(void)
const char *uname;
int i, len;
const __be32 *prop;
+ bool nomap;
int ret;

if (!of_fdt_device_is_available(fdt, child))
@@ -301,6 +302,7 @@ void __init fdt_scan_reserved_mem_late(void)
if (ret && ret != -ENODEV)
continue;

+ nomap = of_get_flat_dt_prop(child, "no-map", NULL) != NULL;
uname = fdt_get_name(fdt, child, NULL);
for (i = 0; i < len; i++) {
u64 b, s;
@@ -310,8 +312,23 @@ void __init fdt_scan_reserved_mem_late(void)
base = b;
size = s;

- if (size)
- fdt_init_reserved_mem_node(child, uname, base, size);
+ if (!size)
+ continue;
+
+ /*
+ * Save only entries that were successfully reserved
+ * in the first pass. Mirrors the preconditions in
+ * early_init_dt_reserve_memory() so that a per-reg
+ * entry failure (outside RAM, or nomap rejected due
+ * to an existing reservation) does not leave a
+ * ghost slot in reserved_mem[].
+ */
+ if (!memblock_overlaps_region(&memblock.memory, base, size))
+ continue;
+ if (nomap && memblock_is_region_reserved(base, size))
+ continue;
+
+ fdt_init_reserved_mem_node(child, uname, base, size);
}
}

--
2.43.0