page fault while in kernel mode

[John Baldwin]

On Monday 20 October 2008 12:32:37 pm Jeremy Chadwick wrote:
> > Forgot to mention I added memory to this server as well, took it from
> > 2GB it was using under 5.4-RELEASE up to 6GB filling all slots, that is
> > why I wanted to load amd64. I reduced down to 4GB and now am able to
> > install 7.0-RELEASE i386. Does this mean that I may have a hardware
> > issue or can FreeBSD produce the page fault I was getting when using
> > over 4GB with i386?
> 
> i386 cannot address more than 4GB unless the kernel is built with PAE
> mode enabled.  This isn't enabled in GENERIC for many (justified)
> reasons.  If you have more than 4GB, you should be using amd64, so you
> made the right decision there.

If you aren't using kernel modules, then PAE should work fine.  You can make 
kernel modules work with PAE as well, but that takes more work.

> > I would love to figure out this BTX halted issue instead...any ideas
> > on that?
> 
> Boot loader problems are difficult to figure out/debug for reasons which
> should be obvious.  I'm CC'ing John Baldwin here, who has experience
> with BTX.  He might be able to shed some light on this.

You will get a BTX fault in 7.0 if your CPU does not support 64-bit "long 
mode" (i.e., amd64).  You can check to see if your CPU does support it by 
looking in the 'AMD features' line of 'dmesg' from an i386 kernel and seeing 
if you have a 'LM' feature.  If you don't, your CPU only supports i386.

-- 
John Baldwin