[PATCH v3 3/3] arm64: acpi: Enable ACPI CCEL support

[Suzuki K Poulose]

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 at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar at kernel.org>
Cc: Steven Price <steven.price at arm.com>
Cc: Sudeep Holla <sudeep.holla at arm.com>
Cc: Gavin Shan <gshan at redhat.com>
Reviewed-by: Gavin Shan <gshan at redhat.com>
Tested-by: Sami Mujawar <sami.mujawar at arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
---
 arch/arm64/kernel/acpi.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index 4d529ff7ba51..b3195b3b895f 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/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;
 
-- 
2.43.0