O.k., no slram as module or in kernel, and RedHat 7.3 is happy.

user-mode-linux/usr/lib/uml/config

@@ -16,8 +16,8 @@ CONFIG_EXPERIMENTAL=y
 #
 # General Setup
 #
-CONFIG_MODE_TT=y
 CONFIG_MODE_SKAS=y
+CONFIG_MODE_TT=y
 CONFIG_NET=y
 CONFIG_SYSVIPC=y
 CONFIG_BSD_PROCESS_ACCT=y
@@ -372,7 +372,7 @@ CONFIG_MTD_BLOCK=y
 # Self-contained MTD device drivers
 #
 # CONFIG_MTD_PMC551 is not set
-CONFIG_MTD_SLRAM=y
+# CONFIG_MTD_SLRAM is not set
 CONFIG_MTD_MTDRAM=m
 CONFIG_MTDRAM_TOTAL_SIZE=4096
 CONFIG_MTDRAM_ERASE_SIZE=128