Re: MTRR driver behavior.

[David Wragg]

<[e-mail]> writes:
> So you're gonna ask ``What kind of a system are you running
> ?''. That's a good question. In fact the system (the one that's
> sluggish) is running a homemade version of BIOS. What I'm suspecting
> here, is that our internally developped BIOS doesn't do any setting to
> the mtrr registers as the Dell BIOS does.  So, even if the Linux mtrr
> driver doesn't see all 3 DIMMS, the system behaves correctly anyway.

The Intel docs say that on reset all the MTRR ranges are disabled. So
if your BIOS doesn't touch them at all, I'm surprised that you see
anthing in /proc/mtrr.

If your BIOS does set them up, but not with settings that match the
memory it detects, then it is broken.  But it wouldn't be the only
BIOS that is broken with regard to MTRRs.

> My question is: is there anything in the mtrr driver that would allow
> me to force the configuration of mtrr registers ?

There is nothing to force the MTRRs to match the memory that the
kernel knows about.  We expect the BIOS to get that much right.

So, unless you want to do some hacking on the mtrr driver, you'll have
to use /proc/mtrr (perhaps you could put together a script to set up
/proc/mtrr based on what it sees in /proc/meminfo).

David Wragg