acpi/prmt: Use EFI runtime sandbox to invoke PRM handlers

Instead of bypassing the kernel's adaptation layer for performing EFI
runtime calls, wire up ACPI PRM handling into it. This means these calls
can no longer occur concurrently with EFI runtime calls, and will be
made from the EFI runtime workqueue. It also means any page faults
occurring during PRM handling will be identified correctly as
originating in firmware code.
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/acpi/Kconfig

@@ -581,7 +581,7 @@ config ACPI_VIOT
 
 config ACPI_PRMT
 	bool "Platform Runtime Mechanism Support"
-	depends on EFI && (X86_64 || ARM64)
+	depends on EFI_RUNTIME_WRAPPERS && (X86_64 || ARM64)
 	default y
 	help
 	  Platform Runtime Mechanism (PRM) is a firmware interface exposing a

drivers/acpi/prmt.c

@@ -260,9 +260,9 @@ static acpi_status acpi_platformrt_space_handler(u32 function,
 		context.static_data_buffer = handler->static_data_buffer_addr;
 		context.mmio_ranges = module->mmio_info;
 
-		status = efi_call_virt_pointer(handler, handler_addr,
-					       handler->acpi_param_buffer_addr,
-					       &context);
+		status = efi_call_acpi_prm_handler(handler->handler_addr,
+						   handler->acpi_param_buffer_addr,
+						   &context);
 		if (status == EFI_SUCCESS) {
 			buffer->prm_status = PRM_HANDLER_SUCCESS;
 		} else {

drivers/firmware/efi/runtime-wrappers.c

@@ -108,6 +108,12 @@ union efi_rts_args {
 		u64		*max_size;
 		int		*reset_type;
 	} QUERY_CAPSULE_CAPS;
+
+	struct {
+		efi_status_t	(__efiapi *acpi_prm_handler)(u64, void *);
+		u64		param_buffer_addr;
+		void		*context;
+	} ACPI_PRM_HANDLER;
 };
 
 struct efi_runtime_work efi_rts_work;
@@ -283,6 +289,13 @@ static void efi_call_rts(struct work_struct *work)
 				       args->QUERY_CAPSULE_CAPS.max_size,
 				       args->QUERY_CAPSULE_CAPS.reset_type);
 		break;
+	case EFI_ACPI_PRM_HANDLER:
+#ifdef CONFIG_ACPI_PRMT
+		status = arch_efi_call_virt(args, ACPI_PRM_HANDLER.acpi_prm_handler,
+					    args->ACPI_PRM_HANDLER.param_buffer_addr,
+					    args->ACPI_PRM_HANDLER.context);
+		break;
+#endif
 	default:
 		/*
 		 * Ideally, we should never reach here because a caller of this
@@ -560,3 +573,21 @@ void efi_native_runtime_setup(void)
 	efi.update_capsule = virt_efi_update_capsule;
 	efi.query_capsule_caps = virt_efi_query_capsule_caps;
 }
+
+#ifdef CONFIG_ACPI_PRMT
+
+efi_status_t
+efi_call_acpi_prm_handler(efi_status_t (__efiapi *handler_addr)(u64, void *),
+			  u64 param_buffer_addr, void *context)
+{
+	efi_status_t status;
+
+	if (down_interruptible(&efi_runtime_lock))
+		return EFI_ABORTED;
+	status = efi_queue_work(ACPI_PRM_HANDLER, handler_addr,
+				param_buffer_addr, context);
+	up(&efi_runtime_lock);
+	return status;
+}
+
+#endif

include/linux/efi.h

@@ -1228,6 +1228,10 @@ extern int efi_tpm_final_log_size;
 
 extern unsigned long rci2_table_phys;
 
+efi_status_t
+efi_call_acpi_prm_handler(efi_status_t (__efiapi *handler_addr)(u64, void *),
+			  u64 param_buffer_addr, void *context);
+
 /*
  * efi_runtime_service() function identifiers.
  * "NONE" is used by efi_recover_from_page_fault() to check if the page
@@ -1247,6 +1251,7 @@ enum efi_rts_ids {
 	EFI_RESET_SYSTEM,
 	EFI_UPDATE_CAPSULE,
 	EFI_QUERY_CAPSULE_CAPS,
+	EFI_ACPI_PRM_HANDLER,
 };
 
 union efi_rts_args;