linux-kernel - Re: [PATCH] x86_64: set cfg_size for AMD Family 10h in case MMCONFIG is used

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Message-ID: <46E97178.2040903@zytor.com>
Date:	Thu, 13 Sep 2007 10:20:56 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
CC:	Andi Kleen <ak@...e.de>, Greg KH <greg@...ah.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jeff Garzik <jeff@...zik.org>, Martin Mares <mj@....cz>,
	dean gaudet <dean@...tic.org>,
	Robert Richter <robert.richter@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86_64: set cfg_size for AMD Family 10h in case MMCONFIG
 is used

Yinghai Lu wrote:
> 
> BIOS guys also said that fam 10h need mmconfig via eax accessing, may
> need OS do sth, so it is safe to stay with MCFG entry for SB like
> mcp55...
> 
> but latest kernel already have that workaround to make mmconfig via eax...
> 

This is actually a good point.  Since the CPU vendor managed to
completely fuck up the operation of MMCONFIG itself on this CPU (it's a
*MEMORY REFERENCE*, guys!), it is actually to be expected and prudent
that BIOS vendors will drop the MCFG entry.  MMCONFIG doesn't actually
work on this CPU for any system software which doesn't already know to
work around this particular piece of severe braindamage;
standards-complicant MMCONFIG isn't supported at all.

	-hpa
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