Patching the Linux kernel to disable the sys_iopl and sys_ioperm system
calls (e.g., by setting CONFIG_GRKERNSEC_IO=y) used to cause the xserver
to fail to start even with KMS-enabled drivers -- at least in the case
of the in-kernel radeon driver.
I don't know what recent changes are responsible but for whatever
reason, X now works fine without the aforementioned system calls on the
same hardware.
Unfortunately, it doesn't work on another machine using the Intel driver
and same X/kernel versions. It fails with the error: "failed to set
IOPL". Does anyone know why the Intel, but not Radeon driver, might be
failing? I don't have any particular knowledge of the inner-workings of
the graphics stack
A quick search turned up the following on the X mailing list: "Fix
initialization when iopl is forbidden":
http://lists.x.org/archives/xorg-devel/2012-September/033656.html
http://cgit.freedesktop.org/~ajax/xserver/patch/?id=d88fb00d791c2b19cf9dd244276838aba3a6b442
The above patch applies to x11-base/xorg-server-1.13.2 (with a fuzz
factor of 2 but it's good) but I haven't had a chance to test it on the
affected machine. I'll post a followup if it fixes the problem.
Dave
