Merge tag 'riscv-for-linus-5.18-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fix from Palmer Dabbelt:

 - A fix to relocate the DTB early in boot, in cases where the
   bootloader doesn't put the DTB in a region that will end up
   mapped by the kernel.

   This manifests as a crash early in boot on a handful of
   configurations.

* tag 'riscv-for-linus-5.18-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  RISC-V: relocate DTB if it's outside memory region

1 files changed, 19 insertions, 2 deletions

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index b0793dc0c291..05ed641a1134 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -208,8 +208,25 @@ static void __init setup_bootmem(void)
 	 * early_init_fdt_reserve_self() since __pa() does
 	 * not work for DTB pointers that are fixmap addresses
 	 */
-	if (!IS_ENABLED(CONFIG_BUILTIN_DTB))
-		memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
+	if (!IS_ENABLED(CONFIG_BUILTIN_DTB)) {
+		/*
+		 * In case the DTB is not located in a memory region we won't
+		 * be able to locate it later on via the linear mapping and
+		 * get a segfault when accessing it via __va(dtb_early_pa).
+		 * To avoid this situation copy DTB to a memory region.
+		 * Note that memblock_phys_alloc will also reserve DTB region.
+		 */
+		if (!memblock_is_memory(dtb_early_pa)) {
+			size_t fdt_size = fdt_totalsize(dtb_early_va);
+			phys_addr_t new_dtb_early_pa = memblock_phys_alloc(fdt_size, PAGE_SIZE);
+			void *new_dtb_early_va = early_memremap(new_dtb_early_pa, fdt_size);
+
+			memcpy(new_dtb_early_va, dtb_early_va, fdt_size);
+			early_memunmap(new_dtb_early_va, fdt_size);
+			_dtb_early_pa = new_dtb_early_pa;
+		} else
+			memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
+	}
 
 	early_init_fdt_scan_reserved_mem();
 	dma_contiguous_reserve(dma32_phys_limit);