thanks a lot, I got kde back.
I used slightly different method as follows
Started suse normally. When blank screen appeared, I pressed ctrl+alt+F3 to start text mode. Logged as root, started startx to get x server. Through yast I disabled autologin. Then I rebooted the computer. When login screen appeared, I changed session type from metacity to kde. Now everything is fine. Now I am going to enable autologin just for convenience.