arm64: acpi: Enable ACPI CCEL support

Add support for ACPI CCEL by handling the EfiACPIMemoryNVS type memory. As per UEFI specifications NVS memory is reserved for Firmware use even after exiting boot services. Thus map the region as read-only. Cc: Sami Mujawar <sami.mujawar@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org> Cc: Steven Price <steven.price@arm.com> Cc: Sudeep Holla <sudeep.holla@arm.com> Cc: Gavin Shan <gshan@redhat.com> Reviewed-by: Gavin Shan <gshan@redhat.com> Tested-by: Sami Mujawar <sami.mujawar@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Will Deacon <will@kernel.org>

Author: Suzuki K Poulose

arch/arm64/kernel/acpi.c

@@ -357,6 +357,16 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
  * as long as we take care not to create a writable
  * mapping for executable code.
  */
+fallthrough;
+
+case EFI_ACPI_MEMORY_NVS:
+/*
+ * ACPI NVS marks an area reserved for use by the
+ * firmware, even after exiting the boot service.
+ * This may be used by the firmware for sharing dynamic
+ * tables/data (e.g., ACPI CCEL) with the OS. Map it
+ * as read-only.
+ */
 prot = PAGE_KERNEL_RO;
 break;