[PATCH v2 4/5] arm64/efi: ignore DT memory nodes instead of removing them

[Ard Biesheuvel]

There are two problems with the UEFI stub DT memory node removal
routine:
- it deletes nodes as it traverses the tree, which happens to work
  but is not supported, as deletion invalidates the node iterator;
- deleting memory nodes entirely may discard annotations in the form
  of additional properties on the nodes.

Now that the UEFI initialization has moved to an earlier stage, we can
actually just ignore any memblocks that are installed after we have
processed the UEFI memory map. This way, it is no longer necessary to
remove the nodes, so we can remove that logic from the stub as well.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
---
 arch/arm64/mm/init.c               | 10 ++++++++
 drivers/firmware/efi/libstub/fdt.c | 24 +-------------------
 2 files changed, 11 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index ab25fde7397c..ecbc051bc66b 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -379,6 +379,16 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 {
 	const u64 phys_offset = __pa(PAGE_OFFSET);
 
+	/*
+	 * This callback will be invoked both when booting via UEFI and when
+	 * booting via DT only. In the former case, we need to ignore memory
+	 * nodes in the DT since UEFI is authoritative when it comes to the
+	 * memory map. So ignore any invocations of this callback after
+	 * EFI_MEMMAP has been set.
+	 */
+	if (efi_enabled(EFI_MEMMAP))
+		return;
+
 	if (!PAGE_ALIGNED(base)) {
 		if (size < PAGE_SIZE - (base & ~PAGE_MASK)) {
 			pr_warn("Ignoring memory block 0x%llx - 0x%llx\n",
diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index ef5d764e2a27..343e7992bd8f 100644
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -24,7 +24,7 @@ efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
 			unsigned long map_size, unsigned long desc_size,
 			u32 desc_ver)
 {
-	int node, prev, num_rsv;
+	int node, num_rsv;
 	int status;
 	u32 fdt_val32;
 	u64 fdt_val64;
@@ -54,28 +54,6 @@ efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
 		goto fdt_set_fail;
 
 	/*
-	 * Delete any memory nodes present. We must delete nodes which
-	 * early_init_dt_scan_memory may try to use.
-	 */
-	prev = 0;
-	for (;;) {
-		const char *type;
-		int len;
-
-		node = fdt_next_node(fdt, prev, NULL);
-		if (node < 0)
-			break;
-
-		type = fdt_getprop(fdt, node, "device_type", &len);
-		if (type && strncmp(type, "memory", len) == 0) {
-			fdt_del_node(fdt, node);
-			continue;
-		}
-
-		prev = node;
-	}
-
-	/*
 	 * Delete all memory reserve map entries. When booting via UEFI,
 	 * kernel will use the UEFI memory map to find reserved regions.
 	 */
-- 
1.9.1