Kernel panic with ACPI enabled

[Nate Lawson]

John Baldwin wrote:
> On Tuesday 07 February 2006 15:13, Donald J. O'Neill wrote:
>>Other things can affect what he's trying to do and cause him to think he
>>has an ACPI problem. I had a bad USB mouse that was causing problems on
>>one of my computers, in fact anything USB on that computer caused a
>>problem with ACPI (it had to be disabled to allow the computer to
>>boot-up) if that mouse was plugged in, until I found the mouse was bad
>>and switched it with one that was ok. On another computer, I could only
>>boot-up if I either disabled ACPI or had the USB mouse unplugged. After
>>it was up, the mouse could be plugged back in and it would work, ACPI
>>would work, but I would be left wondering about the situation. I
>>finally decided to just use a PS-2 mouse and wait a while. That works
>>fine, although I hate ball mice.
> 
> 
> Actually, in his case I'm fairly sure MAXMEM is the problem.  Several people 
> have had problems trying to use the tunable equivalent (hw.physmem=3g and the 
> like) because if the new maxmem value is greater than the highest memory 
> address we found, we just extend the last segment of physical memory.  
> However, in the case of modern machines with SMAPs, this extension can result 
> in including memory that was specifically marked as unavailable (because it 
> was in use by the BIOS to store the ACPI tables) suddenly being used by the 
> kernel.  As part of this process, the kernel does test writes to each page, 
> so it would corrupt the ACPI tables and eventually lead to issues such as 
> this.

Can we at least put a printf() in the boot sequence that says "warning: 
maxmem set and acpi enabled, this may cause problems"?  This keeps 
coming up.

-- 
Nate