Apply affinity subspacing to session requests

base/include/base/affinity.h

@@ -69,6 +69,11 @@ namespace Genode {
 					unsigned height() const { return _height; }
 					unsigned total()  const { return _width*_height; }
 
+					Space multiply(Space const &other) const
+					{
+						return Space(_width*other.width(), _height*other.height());
+					}
+
 					/**
 					 * Return location of a single CPU of specified index
 					 */
@@ -110,6 +115,17 @@ namespace Genode {
 					unsigned width()  const { return _width; }
 					unsigned height() const { return _height; }
 					bool     valid()  const { return _width*_height > 0; }
+
+					Location multiply_position(Space const &space) const
+					{
+						return Location(_xpos*space.width(), _ypos*space.height(),
+						                _width, _height);
+					}
+
+					Location transpose(int dx, int dy) const
+					{
+						return Location(_xpos + dx, _ypos + dy, _width, _height);
+					}
 			};
 
 		private:

base/include/base/child.h

@@ -73,6 +73,17 @@ namespace Genode {
 		                              Server                * /*server*/)
 		{ return false; }
 
+		/**
+		 * Apply session affinity policy
+		 *
+		 * \param affinity  affinity passed along with a session request
+		 * \return          affinity subordinated to the child policy
+		 */
+		virtual Affinity filter_session_affinity(Affinity const &affinity)
+		{
+			return affinity;
+		}
+
 		/**
 		 * Unregister services that had been provided by the child
 		 */

base/run/affinity_subspace.run

@@ -0,0 +1,63 @@
+#
+# \brief  Test to affinity subspacing
+# \author Norman Feske
+#
+
+if {[have_spec platform_pbxa9] || (![have_spec nova] && ![have_spec foc])} {
+	puts "Platform is unsupported."
+	exit 0
+}
+
+
+build "core init test/affinity"
+
+create_boot_directory
+
+install_config {
+	<config>
+		<parent-provides>
+			<service name="LOG"/>
+			<service name="CPU"/>
+			<service name="RM"/>
+			<service name="ROM"/>
+			<service name="RAM"/>
+			<service name="CAP"/>
+			<service name="PD"/>
+			<service name="SIGNAL"/>
+		</parent-provides>
+		<affinity-space width="2" />
+		<default-route>
+			<any-service> <parent/> </any-service>
+		</default-route>
+		<start name="init">
+			<resource name="RAM" quantum="10M"/>
+			<!-- assign the right half of the available CPUs -->
+			<affinity xpos="1" width="1" />
+			<config>
+				<parent-provides>
+					<service name="LOG"/>
+					<service name="CPU"/>
+					<service name="RM"/>
+				</parent-provides>
+				<default-route>
+					<any-service> <parent/> </any-service>
+				</default-route>
+				<!-- assign the leftmost half of CPUs to test-affinity -->
+				<affinity-space width="2" />
+				<start name="test-affinity">
+					<resource name="RAM" quantum="2M"/>
+					<affinity xpos="0" width="1" />
+				</start>
+			</config>
+		</start>
+	</config>
+}
+
+append qemu_args " -nographic -m 64 -smp 8,cores=8 "
+
+build_boot_image "core init test-affinity"
+
+run_genode_until {.*Detected 2x1 CPUs.*} 60
+
+puts "Test succeeded"
+

base/src/base/child/child.cc

@@ -257,6 +257,9 @@ Session_capability Child::session(Parent::Service_name const &name,
 	strncpy(_args, args.string(), sizeof(_args));
 	_policy->filter_session_args(name.string(), _args, sizeof(_args));
 
+	/* filter session affinity */
+	Affinity const filtered_affinity = _policy->filter_session_affinity(affinity);
+
 	/* transfer the quota donation from the child's account to ourself */
 	size_t ram_quota = Arg_string::find_arg(_args, "ram_quota").long_value(0);
 
@@ -274,7 +277,7 @@ Session_capability Child::session(Parent::Service_name const &name,
 
 	/* create session */
 	Session_capability cap;
-	try { cap = service->session(_args, affinity); }
+	try { cap = service->session(_args, filtered_affinity); }
 	catch (Service::Invalid_args)   { throw Service_denied(); }
 	catch (Service::Unavailable)    { throw Service_denied(); }
 	catch (Service::Quota_exceeded) { throw Quota_exceeded(); }

os/include/init/child.h

@@ -658,6 +658,32 @@ namespace Init {
 				_pd_args_policy.   filter_session_args(service, args, args_len);
 			}
 
+			Genode::Affinity filter_session_affinity(Genode::Affinity const &session_affinity)
+			{
+				using namespace Genode;
+
+				/* check if no valid affinity space was specified */
+				if (session_affinity.space().total() == 0)
+					return session_affinity;
+
+				Affinity::Space    const &session_space    = session_affinity.space();
+				Affinity::Location const &session_location = session_affinity.location();
+
+				Affinity::Space    const &child_space    = _resources.affinity.space();
+				Affinity::Location const &child_location = _resources.affinity.location();
+
+				/* scale resolution of resulting space */
+				Affinity::Space space(child_space.multiply(session_space));
+
+				/* subordinate session affinity to child affinity subspace */
+				Affinity::Location location(child_location
+				                            .multiply_position(session_space)
+				                            .transpose(session_location.xpos(),
+				                                       session_location.ypos()));
+
+				return Affinity(space, location);
+			}
+
 			bool announce_service(const char             *service_name,
 			                      Genode::Root_capability root,
 			                      Genode::Allocator      *alloc,