selftests: rds: support RDS built as loadable modules

Commit 92cc6708f4 ("selftests: rds: config: disable modules") set
CONFIG_MODULES=n since run.sh required this kconfig. But disabling
modules also forces every =m option to =n rather than =y, which can
silently drop unrelated features.

This patch removes CONFIG_MODULES=n from the rds selftest config and
updates the check_*conf_enabled() routines to accept a config as
either built-in (=y) or modular (=m). A new probe_module() function
is added to load the backing module when a component is set to be
modular (=m).  config.sh no longer forces CONFIG_MODULES=n, so a user
who follows the SKIP message to run config.sh does not silently end
up with modules disabled again.

rds.ko itself is auto-loaded on socket creation, and rds_rdma.ko is
auto-loaded when SO_RDS_TRANSPORT is set with RDS_TRANS_IB, but the
TCP transport (rds_tcp.ko) is not auto-loaded on the bind path, so
the backing modules are loaded explicitly here.

Signed-off-by: Allison Henderson <achender@kernel.org>
Link: https://patch.msgid.link/20260602050657.26389-4-achender@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/rds/config

@@ -1,4 +1,3 @@
-CONFIG_MODULES=n
 CONFIG_NET_NS=y
 CONFIG_NET_SCH_NETEM=y
 CONFIG_RDS=y

tools/testing/selftests/net/rds/config.sh

@@ -37,9 +37,6 @@ if [[ "$CONF_FILE" != "" ]]; then
 	FLAGS=(--file "$CONF_FILE")
 fi
 
-# no modules
-scripts/config "${FLAGS[@]}" --disable CONFIG_MODULES
-
 # enable RDS
 scripts/config "${FLAGS[@]}" --enable CONFIG_RDS
 scripts/config "${FLAGS[@]}" --enable CONFIG_RDS_TCP

tools/testing/selftests/net/rds/rds_run.sh

@@ -93,38 +93,58 @@ check_gcov_conf()
 	fi
 }
 
+# Checks if a kconfig is enabled (set to =y or =m)
+# $1: kconfig symbol to check
+# $2: (optional) module name backing $1
+#     Ex: check_conf_enabled CONFIG_RDS_TCP rds_tcp
+#     Modules for configs set to  =m will be probed
+#     If omitted, only a built-in (=y) config is accepted.
+# Returns on success.  exits 4 on failure
 # Kselftest framework requirement - SKIP code is 4.
 check_conf_enabled() {
-	if ! grep -x "$1=y" "$kconfig" > /dev/null 2>&1; then
-		echo "selftests: [SKIP] This test requires $1 enabled"
-		echo "Please run tools/testing/selftests/net/rds/config.sh and rebuild the kernel"
-		exit 4
+	if grep -x "$1=y" "$kconfig" > /dev/null 2>&1; then
+		return
 	fi
+	if [ -n "${2:-}" ] && grep -x "$1=m" "$kconfig" > /dev/null 2>&1; then
+		probe_module "$2"
+		return
+	fi
+	echo "selftests: [SKIP] This test requires $1 enabled"
+	echo "Please run" \
+	     "tools/testing/selftests/net/rds/config.sh and rebuild the kernel"
+	exit 4
 }
 
 check_rdma_conf_enabled() {
-	if ! grep -x "$1=y" "$kconfig" > /dev/null 2>&1; then
-		echo "selftests: [SKIP] rdma transport requires $1 enabled"
-		echo "To enable, run " \
-		     "tools/testing/selftests/net/rds/config.sh -r and rebuild"
+	if grep -x "$1=y" "$kconfig" > /dev/null 2>&1; then
+		return
+	fi
+	if [ -n "${2:-}" ] && grep -x "$1=m" "$kconfig" > /dev/null 2>&1; then
+		probe_module "$2"
+		return
+	fi
+	echo "selftests: [SKIP] rdma transport requires $1 enabled"
+	echo "To enable, run" \
+	     "tools/testing/selftests/net/rds/config.sh -r and rebuild"
+	exit 4
+}
+
+# Load the module backing a config that is built as a loadable module
+# (=m).  Built-in (=y) configs are already available and don't reach
+# here.  Exits with the SKIP code if a required module cannot be loaded.
+probe_module() {
+	if ! modprobe -q "$1"; then
+		echo "selftests: [SKIP] could not load required module $1"
 		exit 4
 	fi
 }
 
-check_conf_disabled() {
-	if grep -x "$1=y" "$kconfig" > /dev/null 2>&1; then
-		echo "selftests: [SKIP] This test requires $1 disabled"
-		echo "Please run tools/testing/selftests/net/rds/config.sh and rebuild the kernel"
-		exit 4
-	fi
-}
 check_conf() {
-	check_conf_enabled CONFIG_NET_SCH_NETEM
-	check_conf_enabled CONFIG_VETH
+	check_conf_enabled CONFIG_NET_SCH_NETEM sch_netem
+	check_conf_enabled CONFIG_VETH veth
 	check_conf_enabled CONFIG_NET_NS
-	check_conf_enabled CONFIG_RDS_TCP
-	check_conf_enabled CONFIG_RDS
-	check_conf_disabled CONFIG_MODULES
+	check_conf_enabled CONFIG_RDS_TCP rds_tcp
+	check_conf_enabled CONFIG_RDS rds
 }
 
 # Check kernel config and host environment for RDS-RDMA support.
@@ -139,8 +159,8 @@ check_rdma_conf()
 
 	# Kconfig will enforce CONFIG_INFINIBAND_* as dependencies
 	# of CONFIG_RDMA_RXE
-	check_rdma_conf_enabled CONFIG_RDMA_RXE
-	check_rdma_conf_enabled CONFIG_RDS_RDMA
+	check_rdma_conf_enabled CONFIG_RDMA_RXE rdma_rxe
+	check_rdma_conf_enabled CONFIG_RDS_RDMA rds_rdma
 
 	if ! which rdma > /dev/null 2>&1; then
 		echo "selftests: [SKIP] rdma transport requires the 'rdma'" \