kern/119675: [acpi] apic_hpet0 probe causes divide by zero kernel panic

Nate Lawson nate at
Tue Jan 15 09:20:02 PST 2008

The following reply was made to PR kern/119675; it has been noted by GNATS.

From: Nate Lawson <nate at>
To: Leo Bicknell <bicknell at>
Cc: bug-followup at
Subject: Re: kern/119675: [acpi] apic_hpet0 probe causes divide by zero	kernel
Date: Tue, 15 Jan 2008 08:48:14 -0800

 Leo Bicknell wrote:
 >  In a message written on Tue, Jan 15, 2008 at 10:13:07AM -0500, John Baldwin wrote:
 >  > You can try the patch below.  It fixes a couple of places where we don't
 >  > honor the spec (we don't shut it off in S1 and S2 as required and we don't
 >  > preserve reserved bits in the global configuration register).  It also
 >  > fails the attach if the period is zero which should fix your panic and
 >  > just leave you with no HPET.
 >  Good news and bad news.
 >  With the patch "invalid period" is printed out, so I believe it's
 >  correctly detecting the hpet0 issue.
 >  However, I immediately get an "integer divide fault while in kernel
 >  mode" panic and the boot still fails.  I tried with boot -v and the
 >  message is right after the "invalid period", so I'm not quite sure
 >  what's causing it.
 >  Any recomendations, other than setting up a kernel debugger to see where
 >  it's coming from?
 John's patch should be committed anyway.  However, it's possible your
 panic is happening in non-acpi code.  There's no way to narrow it down
 perfectly without enabled the debugger (options DDB etc.) and typing
 "trace" after it panics.
 However, a boot verbose (boot -v) may give a little more information.

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