stand/lua: Defer kernel/module loading until boot or menu escape

Loading the kernel and modules can be really slow. Loading before the menu
draws and every time one changes kernel/boot environment is even more
painful.

Defer loading until we either boot, auto-boot, or escape to loader prompt.
We still need to deal with configuration changes as the boot environment
changes, but this is generally much quicker.

This commit strips all ELF loading out of config.load/config.reload so that
these are purely for configuration. config.loadelf has been created to deal
with kernel/module loads. Unloading logic has been ripped out, as we won't
need to deal with it in the menu anymore.

Discussed in part with:	allanjude

stand/lua/config.lua

@@ -345,6 +345,9 @@ function config.loadkernel(other_kernel)
 	end
 end
 
+function config.selectkernel(kernel)
+	config.kernel_selected = kernel;
+end
 
 function config.load(file)
 	if (not file) then
@@ -367,9 +370,32 @@ function config.load(file)
 
 	-- Cache the provided module_path at load time for later use
 	config.module_path = loader.getenv("module_path");
+end
+
+-- Reload configuration
+function config.reload(file)
+	-- XXX TODO: We should be doing something more here to clear out env
+	-- changes that rode in with the last configuration load
+	modules = {};
+	config.load(file);
+end
+
+function config.loadelf()
+	local kernel = config.kernel_loaded or config.kernel_selected;
+	local loaded = false;
 
 	print("Loading kernel...");
-	config.loadkernel(config.kernel_loaded);
+	loaded = config.loadkernel(kernel);
+
+	if (not loaded) then
+		loaded = config.loadkernel();
+	end
+
+	if (not loaded) then
+		-- Ultimately failed to load kernel
+		print("Failed to load any kernel");
+		return;
+	end
 
 	print("Loading configured modules...");
 	if (not config.loadmod(modules)) then
@@ -377,30 +403,5 @@ function config.load(file)
 	end
 end
 
-function config.reload(kernel)
-	local kernel_loaded = false;
-
-	-- unload all modules
-	print("Unloading modules...");
-	loader.perform("unload");
-
-	if (kernel ~= nil) then
-		print("Trying to load '" .. kernel .. "'")
-		kernel_loaded = config.loadkernel(kernel);
-		if (kernel_loaded) then
-			print("Kernel '" .. kernel .. "' loaded!");
-		end
-	end
-
-	-- failed to load kernel or it is nil
-	-- then load default
-	if (not kernel_loaded) then
-		print("Loading default kernel...");
-		config.loadkernel();
-	end
-
-	-- load modules
-	config.loadmod(modules);
-end
 
 return config

stand/lua/core.lua

@@ -26,6 +26,8 @@
 -- $FreeBSD$
 --
 
+local config = require('config');
+
 local core = {};
 
 -- Commonly appearing constants
@@ -180,10 +182,12 @@ function core.setDefaults()
 end
 
 function core.autoboot()
+	config.loadelf();
 	loader.perform("autoboot");
 end
 
 function core.boot()
+	config.loadelf();
 	loader.perform("boot");
 end
 

stand/lua/menu.lua

@@ -220,9 +220,7 @@ menu.welcome = {
 			    " of " .. #all_choices .. ")";
 		end,
 		func = function(idx, choice, all_choices)
-			if (#all_choices > 1) then
-				config.reload(choice);
-			end
+			config.selectkernel(choice);
 		end,
 		alias = {"k", "K"}
 	},
@@ -332,6 +330,7 @@ function menu.run(m)
 	if (m == menu.welcome) then
 		screen.defcursor();
 		print("Exiting menu!");
+		config.loadelf();
 		return false;
 	end