A method and apparatus for selectively executing an I/O instruction. The method includes creating an I/O permission bitmap in a memory and receiving an I/O port number and a security context identification (SCID) value. The method also includes using the SCID value and the I/O port number to access the I/O permission bitmap stored to obtain a permission bit corresponding to the I/O port and executing the I/O instruction dependent upon a value of the permission bit corresponding to the I/O port. The I/O permission bitmap includes a plurality of permission bits. Each of the permission bits corresponds to a different one of a plurality of I/O ports. Each of the permission bits has a value indicating whether access to the corresponding I/O port is allowed. The I/O port number indicates the I/O port referenced by the I/O instruction. The SCID value indicates a security context level of a memory location including the I/O instruction.