Re: NetBSD in SIMH vax with 512 MB RAM

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> 2) Since avail_end is added twice to kvmsize (+ some other tables) it
> will overflow the SLR [with 512M of RAM].

> Fixing 2) requires slightly more thinking.  It is really bad and can
> probably cause all sorts of bugs.

Indeed.  Assuming setting SLR too high doesn't itself break anything
(ie, if it's operationally equivalent to setting it to 200000), then
this will probably break as soon as it tries to access anything past
the 1G VM point.

The last thing added to kvmsize in the quoted code is commented as
being the kernel malloc arena, so it depends on the kernel malloc
algorithms; it should break as soon as kernel malloc tries to place
anything past 0xbfffffff.

> Another way would be to limit the physical memory to 256M and add
> support to not map all of physical memory for large-memory machines
> as a compile-time option.

I'd say the rightest thing to do is compute - either mechanically or by
hand - what amount of physical memory would put SLR as close as
possible to 200000 without going over, then cap physical memory size at
that value (preferably with a message).

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