From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <60919fa8d3da2efc099c84c83b1c54cd@plan9.bell-labs.com>
From: jmk@plan9.bell-labs.com
To: 9fans@cse.psu.edu
Subject: Re: [9fans] The details on the kernel panic!
In-Reply-To: <BAY8-F69Yoo9tjxqxPs0004b006@hotmail.com>
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Date: Wed, 10 Mar 2004 11:46:01 -0500
Topicbox-Message-UUID: 2885fb62-eacd-11e9-9e20-41e7f4b1d025

You would find the answer to this if you looked back far enough in the
archives. The BIOS has placed the framebuffer physical address at a place
where, when converted to a virtual address by the kernel using a one-to-one
mapping stating at 0x80000000, it clashes with allocated physical memory.
E.g.
	physical memory goes from 0 to 0x20000000 (512MB);
	kernel maps this to virtual by or'ing with 0x80000000, thus kernel
		virtual memory goes from 0x80000000 to 0xA0000000;
	the framebuffer physical address is 0x90100000;
	the kernel tries to map that to a virtual address
		(0x80000000|0x90100000 == 0x90100000) and finds it already has
		a mapping for that virtual address;
	boom.

Sometimes, depending on the model of graphics chip, you can bypass this by
deleting the 'linear=1' option in the vgadb entry for the controller, but
I don't think that's possible with this controller.

It's possible the base address of the framebuffer could be changed with this
chip, but I'm not familiar with it and don't have one to try.

This needs a rewrite of the MMU code on the x86, which needs to be done for
other reasons, but I've had on my list for >5 years. It's not going to happen
soon. Sorry.

--jim


On Wed Mar 10 10:50:51 EST 2004, zbxhfhxha@hotmail.com wrote:
> Ok, I tried Plan9 on my Thinkpad R31 laptop.. Specs are:
> Intel Ethernet card
> Intel i810/830M video card
> Pentium 3 1.15Ghz (around that much)
> 512MB Ram
> 30GB HDD
> 
> Now, I tried to choose 'Install Plan9 from this CD' and I got prompted about 
> the mouse and video resolution, though before that, I got..
> init: starting /bin/rc
> echo: write error: bad process or channel control request
> Now, after setting it up, both default and when I customized it, I get the 
> panic...
> panic: mmukmap1: p
> panic: mmukmap1: pa 90100000 entry 10000183
> I get the same thing when trying to boot from CD rather than install though 
> /bin/rc started properly..
> Can anyone tell me what I'm doing wrong or how to fix this?
> I hope someone can help..
> Thanks alot.
> 
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