More trapframe panics

[Juli Mallett]

On Sun, Jan 26, 2014 at 7:07 AM, Jan Bramkamp <crest at rlwinm.de> wrote:
>
> Would increasing KSTACK_PAGES from two to three or four help? What are
> the trade-offs involved in choosing KSTACK_PAGES for something like the
> EdgeMax Lite?


That's exactly what needs to happen in all 64-bit MIPS kernels.  Unlike
some other architectures,  KSTACK_PAGES cannot simply be increased,
however.  All of the code which handles loading the kernel stack and
keeping it mapped, etc., assumes that it takes up exactly one TLB entry,
i.e. 2 pages.  One could simply double KSTACK_PAGES for 64-bit builds and
modify the code to support the case of 2 or 4 pages, which would keep the
code as gross as it is today and not buy much flexibility, but might be
worthwhile as a short-term fix.  Being able to support arbitrary values of
KSTACK_PAGES (or at least arbitrary multiples of 2 up to the maximum number
of wired TLB entries times 2) would be better.

Thanks,
Juli.