Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fix from Catalin Marinas:
 "A previous commit to prevent AML memory opregions from accessing the
  kernel memory turned out to be too restrictive. Relax the permission
  check to permit the ACPI core to map kernel memory used for table
  overrides"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: permit ACPI core to map kernel memory used for table overrides

1 files changed, 20 insertions, 2 deletions

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index a85174d05473..cada0b816c8a 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -298,8 +298,21 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
 		case EFI_BOOT_SERVICES_DATA:
 		case EFI_CONVENTIONAL_MEMORY:
 		case EFI_PERSISTENT_MEMORY:
-			pr_warn(FW_BUG "requested region covers kernel memory @ %pa\n", &phys);
-			return NULL;
+			if (memblock_is_map_memory(phys) ||
+			    !memblock_is_region_memory(phys, size)) {
+				pr_warn(FW_BUG "requested region covers kernel memory @ %pa\n", &phys);
+				return NULL;
+			}
+			/*
+			 * Mapping kernel memory is permitted if the region in
+			 * question is covered by a single memblock with the
+			 * NOMAP attribute set: this enables the use of ACPI
+			 * table overrides passed via initramfs, which are
+			 * reserved in memory using arch_reserve_mem_area()
+			 * below. As this particular use case only requires
+			 * read access, fall through to the R/O mapping case.
+			 */
+			fallthrough;
 
 		case EFI_RUNTIME_SERVICES_CODE:
 			/*
@@ -388,3 +401,8 @@ int apei_claim_sea(struct pt_regs *regs)
 
 	return err;
 }
+
+void arch_reserve_mem_area(acpi_physical_address addr, size_t size)
+{
+	memblock_mark_nomap(addr, size);
+}