Unlike JTAG, the SelectMAP configuration interface seems to be equivalent to the ICAP (Internal Configuration Access Port), which has already been succeesfully used for partial reconfiguration with Spartan-6 (as opposed to the JTAG interface).

The pinout of the Spartan-6 LX9 TQG144 is in [UG385] in table 2-2, p.28 (v2.2):

M0: P69
M1: P60

D0: P65
D1: P62
D2: P61
D3: P46
D4: P45
D5: P44
D6: P43
D7: P48

CSI_B: P64
RDWR_B: P47
CCLK: P70
PROGRAM_B: P37
DONE: P71
INIT_B: P39

Unfortunately, on my board, those pins are not easy to reach, since they are "hard-connected" to other chips or bound to Vcc/GND.

[UG385]

Spartan-6 FPGA Packaging and Pinouts http://www.xilinx.com/support/documentation/user_guides/ug385.pdf