reproducable "panic: pmap_enter: attempted pmap_enter on 4MB page"

[Andrew Gallatin]

Sam Leffler writes:
 > On Mar 5, 2004, at 8:22 AM, Andrew Gallatin wrote:
 > 
 > I've been getting this panic off+on for >9 months but haven't been able 
 > to characterize it and/or narrow down the cause.  I mostly see it on an 
 > NFS server.

For me it seemed to always happen when a particular kva was used.
(0xc86ce000).  It did not matter if I used my real driver, or a
contrived 20-line test case that just malloc'ed a bunch of memory at
module load.  As soon as pmap_enter() was called on that kva, kaboom!

But this behaviour stopped when:

a) I changed from a non-WITNESS, non-INVARIANTS kernel to a
   WITNESS and INVARIANTS kernel.
a) I upgraded kernel sources from Weds -> Fri


It almost smells like something size related.   Eg, something is
overflowing and corrupting the page tables when the kernel has
a particular size or alignment.

I'm just curious -- when this happens to you, is it the same KVA
that I saw?  There is a printf just before the panic which
spits out the kva..

Drew