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SubjectRe: [Fastboot] [CFT] ELF Relocatable x86 and x86_64 bzImages
On Sat, Aug 12, 2006 at 01:20:29AM -0600, Eric W. Biederman wrote:
> Don Zickus <dzickus@redhat.com> writes:
>
> >> >>
> >> >> I'm a little disappointed but at this point it isn't a great surprise,
> >> >> the code is early yet and hasn't had much testing or attention.
> >> >> I wonder if I have missed something else silly.
> >> >>
> >> >> As for testing, can you use plain kexec to load the kernel at a
> >> >> different address? I'm curious to know if it is something related
> >> >> to the kexec on panic path or if it is just running at a different
> >> >> location that is the problem.
> >> >
> >
> > I think I have found the 'something silly'. Here is a patch that allows
> > our Dell em64t boxes to boot. This change matches the original code. The
> > main difference that caused the problems was the setting of _PAGE_NX bit.
> > This caused issues in early_io_remap().
> >
> > Thanks to Larry Woodman for debugging this.
>
> This looks like a different one but looks fairly sane.
>
> Do you know what code had problems having _PAGE_NX set.
> What are we doing with early_ioremap the requires execute
> permissions. It doesn't sound right that we would need
> this.

This fix is only needed for a subset of our em64t boxes, so it could be
just a chipset problem. Supposedly, if I remember the conversation
correctly, when the kernel first boots it reserves about 40MB and about 20
pmds automatically. After decompression, early_io_remap tries to setup
all the memory. The conflict arose when early_io_remap tried to reuse one
of those pmds. This caused the system to crash and reboot.

I'll try to get more info Monday on the specifics.

Cheers,
Don

>
> Eric
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