Subject: [PATCH v3 07/11] of: reserved_mem: save /memreserve/ entries into the reserved_mem array

From: Wandun Chen <[email-masked]>
Date: Wed, 27 May 2026 11:29:13 +0800

From: Wandun Chen <[email-masked]>

/memreserve/ is used by firmware or bootloaders, such regions hold no
useful data for crash analysis, they should be excluded from the
kdump vmcore, so save /memreserve/ entries into the reserved_mem array
for later exclusion.

If a /memreserve/ entry overlaps any dumpable reserved region, mark
the whole memreserve entry dumpable as well. This may keep slightly
more memory in vmcore than strictly necessary, but avoids splitting
entries and never drops data that may be useful for crash analysis.

Signed-off-by: Wandun Chen <[email-masked]>
Tested-by: Meijing Zhao <[email-masked]>
---
 drivers/of/fdt.c             |  4 +++
 drivers/of/of_private.h      |  2 ++
 drivers/of/of_reserved_mem.c | 55 ++++++++++++++++++++++++++++++++++++
 3 files changed, 61 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 83a2a474831e..745e53b1c564 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -499,6 +499,7 @@ void __init early_init_fdt_scan_reserved_mem(void)
 	int n;
 	int res;
 	u64 base, size;
+	int nr_memreserve = 0;
 
 	if (!initial_boot_params)
 		return;
@@ -516,7 +517,9 @@ void __init early_init_fdt_scan_reserved_mem(void)
 		if (!size)
 			break;
 		memblock_reserve(base, size);
+		nr_memreserve++;
 	}
+	fdt_reserved_mem_account_memreserve(nr_memreserve);
 }
 
 /**
@@ -1288,6 +1291,7 @@ void __init unflatten_device_tree(void)
 	if (fdt && alloc_reserved_mem_array()) {
 		/* Save the statically-placed regions in the reserved_mem array */
 		fdt_scan_reserved_mem_late();
+		fdt_reserved_mem_save_memreserve_entries();
 	}
 
 	/* Populate an empty root node when bootloader doesn't provide one */
diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
index 50e5a533e059..30954e859689 100644
--- a/drivers/of/of_private.h
+++ b/drivers/of/of_private.h
@@ -188,6 +188,8 @@ static inline struct device_node *__of_get_dma_parent(const struct device_node *
 int fdt_scan_reserved_mem(void);
 void __init fdt_scan_reserved_mem_late(void);
 bool __init alloc_reserved_mem_array(void);
+void __init fdt_reserved_mem_account_memreserve(int n);
+void __init fdt_reserved_mem_save_memreserve_entries(void);
 
 bool of_fdt_device_is_available(const void *blob, unsigned long node);
 
diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 888dcb6bdce5..5e27f9403786 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -248,6 +248,43 @@ static void __init __rmem_check_for_overlap(void)
 	}
 }
 
+static void __init fdt_reserved_mem_add_memreserve(phys_addr_t base,
+						   phys_addr_t size)
+{
+	struct reserved_mem *rmem;
+	bool dumpable = false;
+	int i;
+
+	if (reserved_mem_count == total_reserved_mem_cnt) {
+		pr_err("not enough space for memreserve regions.\n");
+		return;
+	}
+
+	for (i = 0; i < reserved_mem_count; i++) {
+		rmem = &reserved_mem[i];
+
+		if (!rmem->dumpable)
+			continue;
+
+		if (base < rmem->base + rmem->size && rmem->base < base + size) {
+			dumpable = true;
+			break;
+		}
+	}
+
+	rmem = &reserved_mem[reserved_mem_count];
+	rmem->base = base;
+	rmem->size = size;
+	rmem->dumpable = dumpable;
+
+	reserved_mem_count++;
+}
+
+void __init fdt_reserved_mem_account_memreserve(int n)
+{
+	total_reserved_mem_cnt += n;
+}
+
 /**
  * fdt_scan_reserved_mem_late() - Scan FDT and initialize remaining reserved
  * memory regions.
@@ -305,6 +342,24 @@ void __init fdt_scan_reserved_mem_late(void)
 	__rmem_check_for_overlap();
 }
 
+void __init fdt_reserved_mem_save_memreserve_entries(void)
+{
+	const void *fdt = initial_boot_params;
+	u64 base, size;
+	int n;
+
+	if (!fdt)
+		return;
+
+	for (n = 0; ; n++) {
+		if (fdt_get_mem_rsv(fdt, n, &base, &size))
+			break;
+		if (!size)
+			break;
+		fdt_reserved_mem_add_memreserve(base, size);
+	}
+}
+
 static int __init __reserved_mem_alloc_size(unsigned long node, const char *uname);
 
 /*
-- 
2.43.0