Does anyone undefine APM_RELAX_SEGMENTS?

[Zachary Amsden <zach@vmware.com>]

Rohit Seth wrote:

> On Thu, 2005-11-10 at 00:23 -0800, akpm@osdl.org wrote:
>  
>
> > The patch titled
> >
> >     x86: Always relax segments
> >
> > has been added to the -mm tree.  Its filename is
> >
> >     x86-always-relax-segments.patch
> >
> >
> > From: Zachary Amsden <zach@vmware.com>
> >
> > APM BIOSes have many bugs regarding proper representation of the appropriate
> > segment limits for calling the BIOS.  By default, APM_RELAX_SEGMENTS is always
> > turned on to support running the APM BIOS on these buggy machines.  Keeping
> > 64k limits poses very little danger to the kernel, because the pages where the
> > APM BIOS is located will always be in low physical memory BIOS areas, which
> > should already be marked reserved, and only buggy BIOSes would possibly
> > overstep the segment bounds with writes to data anyway.
> >
> > Since forcing stricter limits breaks many machines and is not default
> > behavior, it seems reasonable to deprecate the older code which may cause APM
> > BIOS to fault.
> >
> >    
> But I presume it make some other machines to work?
>  
It would make the APM thread panic on machines with broken APM BIOS - 
which is not very useful except for proving a BIOS bug.  But APM is 
inherently safer than PnP, since there is no transfer segment which can 
corrupt arbitrary kernel memory.
In the history of its introduction, I can not find a single distribution 
or use which undefines this macro.  If anyone knows otherwise, please 
advise.
Zach
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