Add qemu commandline environment variable support. (#961)

Make it easier to tweak some qemu options by allowing passthru of
command line environment variables.

- Also cleans up weird variable indirection used for qemu commandline args
  variable through `qargs` in various constructors.
- Addresses some functionality discussed in #776.

lib/vagrant-libvirt/action/create_domain.rb

@@ -110,6 +110,12 @@ module VagrantPlugins
           @redirdevs = config.redirdevs
           @redirfilters = config.redirfilters
 
+          # Additional QEMU commandline arguments
+          @qemu_args = config.qemu_args
+
+          # Additional QEMU commandline environment variables
+          @qemu_env = config.qemu_env
+
           # smartcard device
           @smartcard_dev = config.smartcard_dev
 
@@ -322,15 +328,22 @@ module VagrantPlugins
             env[:ui].info(" -- smartcard device:  mode=#{@smartcard_dev[:mode]}, type=#{@smartcard_dev[:type]}")
           end
 
-          @qargs = config.qemu_args
-          if not @qargs.empty?
+          unless @qemu_args.empty?
             env[:ui].info(' -- Command line args: ')
-            @qargs.each do |arg|
+            @qemu_args.each do |arg|
               msg = "    -> value=#{arg[:value]}, "
               env[:ui].info(msg)
             end
           end
 
+          unless @qemu_env.empty?
+            env[:ui].info(' -- Command line environment variables: ')
+            @qemu_env.each do |env_var, env_value|
+              msg = "    -> #{env_var}=#{env_value}, "
+              env[:ui].info(msg)
+            end
+          end
+
           env[:ui].info(" -- Command line : #{@cmd_line}") unless @cmd_line.empty?
 
           # Create Libvirt domain.

lib/vagrant-libvirt/config.rb

@@ -165,6 +165,9 @@ module VagrantPlugins
       # Additional qemuargs arguments
       attr_accessor :qemu_args
 
+      # Additional qemuenv arguments
+      attr_accessor :qemu_env
+
       # Use QEMU session instead of system
       attr_accessor :qemu_use_session
 
@@ -284,7 +287,12 @@ module VagrantPlugins
         # Attach mgmt network
         @mgmt_attach       = UNSET_VALUE
 
-        @qemu_args  = []
+        # Additional QEMU commandline arguments
+        @qemu_args         = UNSET_VALUE
+
+        # Additional QEMU commandline environment variables
+        @qemu_env          = UNSET_VALUE
+
         @qemu_use_session  = UNSET_VALUE
       end
 
@@ -599,9 +607,17 @@ module VagrantPlugins
       end
 
       def qemuargs(options = {})
+        @qemu_args = [] if @qemu_args == UNSET_VALUE
+
         @qemu_args << options if options[:value]
       end
 
+      def qemuenv(options = {})
+        @qemu_env = {} if @qemu_env == UNSET_VALUE
+
+        @qemu_env.merge!(options)
+      end
+
       # code to generate URI from a config moved out of the connect action
       def _generate_uri
         # builds the Libvirt connection URI from the given driver config
@@ -788,7 +804,11 @@ module VagrantPlugins
         # Attach mgmt network
         @mgmt_attach = true if @mgmt_attach == UNSET_VALUE
 
+        # Additional QEMU commandline arguments
         @qemu_args = [] if @qemu_args == UNSET_VALUE
+
+        # Additional QEMU commandline environment variables
+        @qemu_env = {} if @qemu_env == UNSET_VALUE
       end
 
       def validate(machine)
@@ -824,6 +844,10 @@ module VagrantPlugins
           c = cdroms.dup
           c += other.cdroms
           result.cdroms = c
+
+          c = qemu_env != UNSET_VALUE ? qemu_env.dup : {}
+          c.merge!(other.qemu_env) if other.qemu_env != UNSET_VALUE
+          result.qemu_env = c
         end
       end
     end

lib/vagrant-libvirt/templates/domain.xml.erb

@@ -266,11 +266,14 @@
     <% end %>
   </devices>
 
-  <% unless @qargs.empty? %>
+  <% if not @qemu_args.empty? or not @qemu_env.empty? %>
   <qemu:commandline>
-    <% @qargs.each do |arg| %>
+    <% @qemu_args.each do |arg| %>
     <qemu:arg value='<%= arg[:value] %>'/>
     <% end %>
+    <% @qemu_env.each do |env_var, env_value| %>
+    <qemu:env name='<%= env_var.to_s %>' value='<%= env_value %>'/>
+    <% end %>
   </qemu:commandline>
   <% end %>
 </domain>