Only one hart is exposed to gdb

[Disasm]

My openocd config:

transport select jtag
adapter_khz 1000

set _CHIPNAME riscv
jtag newtap $_CHIPNAME cpu -irlen 5 -expected-id 0x04e4796b

set _TARGETNAME $_CHIPNAME.cpu
target create $_TARGETNAME riscv -chain-position $_TARGETNAME

init
halt

gdb output:

...
(gdb) target remote :3333
Remote debugging using :3333
warning: No executable has been specified and target does not support
determining executable automatically.  Try using the "file" command.
0x0000000088001a40 in ?? ()
(gdb) info threads
  Id   Target Id         Frame 
* 1    Remote target     0x0000000088001a40 in ?? ()

Is there any way to access second hart for debugging?

[GongT]

-m 1 argument