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SubjectRe: Load linux...from linux? (fwd)
continuing the linux-loads-linux discussion. Werner's new code is quite
cool. I'm somewhat concerned about turning off PTEs during the process. I
did a bit of work in LOBOS to leave all the VM hardware on. My worries are
probably groundless ...

as for linuxbios, I'm now into debugging start_kernel. I haven't got
interrupts turned on right (it's somewhat harder from a hard reset) but
hope to have that worked out later today.

ron

---------- Forwarded message ----------
Date: Tue, 29 Feb 2000 19:35:16 +0100 (MET)
From: Werner Almesberger <almesber@lrc.epfl.ch>
To: Ronald G. Minnich <rminnich@lanl.gov>
Subject: Re: Load linux...from linux?

Ronald G. Minnich wrote:

> Your code is very nice.

Thanks ! ;-) BTW, I've made a new version which should raise the limit
for loaded data to 2GB:

ftp://icaftp.epfl.ch/pub/people/almesber/misc/bootimg-1.tar.gz

Now I need to build a kernel >> 1 GB to actually test this ...

> Question: If I have 1 GB or less there's no issue with addressing all of
> physical memory from the current kernel virtual address space.

Yep, your approach is limited to the kernel address space. Not sure if
this is really a problem, though:

- vmalloc should always give you pages you can reach from the kernel
- I don't think any architecture puts boot code beyond the kernel
address space (it could make a little bit of sense for things like
initrd, but then, any solution requiring multi-gigabyte initrds is
at least suspicious, I'd say ;-)
- 1 GB for kernel, initrd, parameters, and friends should be
sufficient for most practical purposes.

> Also I'd like to leave some hook in there for continuing with the page
> table usage because the next step is the Alpha.

What are actually the requirements on the Alpha ? Does the kernel expect
to be started with page tables already set up ? If not, is there no way
to simply turn off paging ? In my approach, one could add some page
tables to the "sacred" pages, if necessary, but it's a little ugly.

- Werner

--
_________________________________________________________________________
/ Werner Almesberger, ICA, EPFL, CH werner.almesberger@ica.epfl.ch /
/_IN_N_032__Tel_+41_21_693_6621__Fax_+41_21_693_6610_____________________/


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