Re: x86: runtime waring in pcibios_fwaddrmap_lookup

[Meelis Roos <mroos@linux.ee>]

> So, somehow, your system hit the assertion (WARN_ON) in
> pcibios_fwaddrmap_lookup().  From the dmesg log you provided I can see
> why pcibios_save_fw_addr() was called - there is a resource collision
> with the video device's GART - but what I don't understand is how the
> assertion is being triggered.
> 
> There are only two callers of pcibios_fwaddrmap_lookup()
> (see ./arch/x86/pci/i386.c:: pcibios_save_fw_addr(), and
> pcibios_retrieve_fw_addr()) and both of those are acquiring the lock
> before making the call - so triggering the assertion just doesn't seem
> possible but obviously it is getting triggered.
> 
> I don't have any ideas currently but do have some questions that
> hopefully will start to enlighten us.
> 
>         Does your system encounter this consistently upon every boot or
>         is it hit intermittently?

Every time.

>         Do you know of any kernel versions that do not encounter it?

Checked my logs, no kernel up to 3.3.0 included gave it, next tested 
kernel was 3.4.0-rc2 and that had the warning and every kernel since has 
had it.

>         Are you running a para-virtualized kernel?

No.

-- 
Meelis Roos (mroos@ut.ee)      http://www.cs.ut.ee/~mroos/