OpenBSD's GENERIC kernels have all support for running X enabled.
The server supports wscons, the standard OpenBSD/i386 console driver.
By default OpenBSD includes the BSD 4.4 kernel security
feature that disables access to the /dev/mem device when in
multi-user mode. But the X server requires
linear access to the display memory in most cases.
OpenBSD requires the aperture driver to be enabled for all X servers, because the aperture driver also controls access to the I/O ports of the video boards.
To enable the aperture driver, once included in the kernel, set
machdep.allowaperture=2
/etc/sysctl.conf. See the
xf86(4)
manual page for details.
Another (less recommended) way to enable linear memory and I/O ports
access is to disable the kernel security feature by
initializing securelevel to -1 in /etc/rc.securelevel.
Caveat: the aperture driver only allows one access at a time
(so that the system is in the same security state once X is
launched). This means that if you run multiple servers on multiple
virtual terminals, only the first one will have linear memory access.
Set securelevel to -1 if you need more that one X server at a time.
OpenBSD supports System V shared memory. If X detects this support in your kernel, it will support the MIT-SHM extension.