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Re: Fedora Core 2 won't recompile to run AGP, NVIDIA



On Thu, Dec 09, 2004 at 08:59:42PM -0500, John Burns wrote:

 > Right now, I post from a working install of Fedora 2, running a 
 > 2.6.9-1.6_FC2 prebuilt kernel. After many hours of researching why 
 > xorg.conf setting nvAGP failed under "1" (NVIDIA internal AGP) but 
 > succeeded under "3" (agpgart) I determined that Fedora developers 
 > compiled agpgart into the kernel, for whatever reason.

There are several reasons.
One of which is that out-of-tree agpgart implementations, as found
in certain binary drivers are _dangerous_ when used on amd64 for
example, as they have no idea whether or not the IOMMU code
has started using the agp aperture.  This is dangerous as any
graphics code that starts trying to use the first half of the
aperture stomps all over any existing mappings, which could be
in-flight IO requests.

Additionally, code such as the Intel i8xx framebuffer need
the agpgart to initialise before it does.

 > Going monolithic 
 > seems to defeat the purpose of modules, and they should know that people 
 > might want to use NVIDIA's AGP, to compare the feel and performance.

There should be very little difference (if any) between the two.

 > Somewhat angry, I spent many hours trying to compile both this kernel 
 > and 2.6.5-1.358. My primary goal was to be able to use NVIDIA's internal 
 > AGP, instead of the kernel.. My secondary goal was to see how a stripped 
 > down kernel would perform. There are many things compiled into those 
 > kernels that I don't need for a modest system: AMD XP 1800, 384 MB RAM, 
 > cheap legacy GeForce2 MX/MX 400
 > 
 > Bottom line: all attempts to build a kernel with running AGP support 
 > failed. The modules seem to build. The NVIDIA drivers build (6629, 6610) 
 > But AGP won't initialize!! When AGP support is built as module, it 
 > fails.
 > I get X, but no proc/status list of success.

agpgart creates no /proc entries. Ever, and never has.

 > I have to tools and instructions to build a kernel. I used the .config 
 > from the pre-made Fedora kernels that have "working" AGP (never using 
 > NVIDIA's internal system, but kernel agpgart) Asside from leaving out 
 > totally irrelevant modules and features, my only deviation from those 
 > configs was to config for AMD K-6 (instead of "Pentium Pro" under 
 > xconfig) I don't have a Pentium. This should have been safe.

(which was suboptimal for your Athlon btw. K6 is a 586 era CPU).
Pentium Pro was actually closer to your target arch, athlon being
the exact match.

 > Does anyone know why the sources seem broken with respect to AGP?

Worksforme.  Though I don't use the NVidia module, which could be a hint
as to whats broken.

 > I'm willing to forgive being forced to use agpgart if I could run a 
 > stripped down Fedora kernel. All the other features worked, the boot 
 > speed was FAST, and the RAM imprint was 30-40 MB less (a huge decrease)

That is very strange. Building all the modules that the Fedora kernel
carries shouldn't make *any* difference at all, as only ones that match
your hardware get loaded, and I find it hard to believe you had 30-40MB
of modules loaded with the Fedora kernel. Of the 38 modules my laptop
has loaded right now, it totals just over 1.7MB of resident code.

 > Were the released, prebuilt kernels rigged in undocumented ways to get 
 > NVIDIA AGP support working?

no

		Dave


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