Thanks for your answer.
But this folder does not contain any file with a function prototype ibv_create_qp.
There is ib_al interface.
But I search for an interface used in example 'rc_pingpong' supplied with WOF3-2-1 (WOF3-2-1\GA\ulp\libibverbs).
This example uses function 'ibv_create_qp'.
I do not know if there is a relation between this example and utility 'ibv_rc_pingpong.exe' (from folder 'Program Files\Mellanox\MLNX_VPI\IB\Tools')
but it appears that this utility depends on DLL system32\libibverbs.dll (installed by driver Mellanox WinOF 5.22).
So libibverbs.dll exists but I cannot find a header to use this DLL in my programs.
The header from WOF3-2-1 looks like to be old for this DLL (it looks like there are ABI problems).
Is there any idea where to find this header?