linux-kernel - Re: fpu IO port reservation (arch/i386)

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Message-ID: <Pine.LNX.4.64N.0709241235490.22491@blysk.ds.pg.gda.pl>
Date:	Mon, 24 Sep 2007 12:42:20 +0100 (BST)
From:	"Maciej W. Rozycki" <macro@...ux-mips.org>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Peter Fordham <peter.fordham@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: fpu IO port reservation (arch/i386)

On Fri, 21 Sep 2007, Andi Kleen wrote:

> >  For the curious the details of all the hassle are reasonably well 
> > described in the Intel's AP-578 application note.
> 
> Thanks. Ok it has to stay for for i386 then; although it would be in theory
> possible to only reserve when the CPU is a real 386. For x86-64 it's
> gone now.

 For anything newer the latch is still there in the chipset; most likely 
in the south bridge and probably actively decoded (irrespective of the 
architecture of the bit behind the north bridge) though it may be possible 
to disable it in a chip-specific manner.  If there is no south bridge in a 
given system, then it is probably safe not to claim the port.

  Maciej
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