[Xorg-driver-geode] X failure under LinuxBIOS

[Bart Trojanowski]

* Jordan Crouse <jordan.crouse at amd.com> [080128 13:17]:
> On 28/01/08 12:05 +0200, Martin-Éric Racine wrote:
> > As the attached file shows, running "X -configure" fails on a Geode LX
> > booting from LinuxBIOS. This is against the current AMD driver 2.7.7.6
> > and X server 1.3 patched with Bart's x86emu fixes.
> 
> > 2: /usr/lib/xorg/modules//libint10.so(x_outb+0x3a) [0xb77ae76a]

This is probably caused by my "blacklist for I/O port in 0-0xFF range"
patch.

http://www.jukie.net/~bart/patches/xorg-server/20080111/0001-X86EMU-added-blacklist-for-I-O-port-in-0-0xFF-range.patch

The patch throws an exception (by sending a SIGSEV) to itself.

> > Emulator asked to make a suspect byte access to port 0 (0x0000); terminating.

The blacklist is a good thing, because accessing those ports could be
fatal.  In this case there is a write on port 0.  This port is "DMA
channel 0 current address", and user space code should not have access
to the DMA engines w/o going through the kernel.

The BIOS is either doing something new that we need to emulate, or there
is another bug ...

> Uh, oh - thats not good.  Why does it think it has VGA?

... in the driver or x-core that causes this access indirectly.  I have
not looked at the code yet, but addressing Jordan's question may be
easier then emulating a DMA engine.

-Bart

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