Any way to limit available memory? [5.2.1-R-p5]

[Don Bowman]

From: John Kennedy [mailto:jk at jk.homeunix.net]
> It looks like one of my Dell boxes has some memory that is 
> accessible but
> shouldn't be.  Sort of peculiar in that it:
> 
>     1: Is .2MB in from the upper memory limit, and changes when
> 	available memory changes
>     2: Isn't slot or memory-stick dependent
>     3: Can lock the machine up solid when you write certain data
> 	patterns to it
>     4: Doesn't seem to be OS-dependent (Memtest86 ISO, FreeBSD)
> 
> Between the data corruption (segmentation violations, 
> mostly), the memory
> location (we tend to have problems after the machine has been up and
> thrashing for a while) and the symptoms (periodic solid 
> lockups) it looks
> like this may be the smoking gun for some of the problems 
> we've been seeing
> on that machine.
> 
> I'll obviously be pursuing some solutions in the near future (BIOS
> upgrades, Dell hardware diagnostics, hard-coding available memory for
> operating system, etc).
> 
> For the short term, however, is there some way to get the 
> system to think
> that we have ~1MB less RAM than it actually tests for?

This is the SMM [System Management Mode].
Its owned by a special virtual machine.

You can set hw.physmem= to restrict access.