linux-kernel - Re: [PATCH] X86: fix typo PAT to X86

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Message-ID: <20080118185635.GD10167@redhat.com>
Date:	Fri, 18 Jan 2008 13:56:35 -0500
From:	Dave Jones <davej@...hat.com>
To:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Yinghai Lu <Yinghai.Lu@....COM>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] X86: fix typo PAT to X86_PAT

On Fri, Jan 18, 2008 at 10:47:05AM -0800, Venki Pallipadi wrote:

 > >This exclusion is going to be a real pain in the ass for 
 > >distro kernels.
 > >It's impossible for example to build a kernel that will now support
 > >the MTRR-alike registers on the AMD K6/early Cyrix etc and also
 > >support PAT.
 > 
 > Actually, this exclusion will not work at all with the current code.
 > Infact it should be PAT selects MTRR, for the current code. As
 > pat_init() is called during mtrr init as the rules for how to change PAT
 > and how to change MTRR are same. Further, MTRR is always required on
 > SMP, as we read the MTRR setting from boot CPU and set it on Aps at boot
 > time. We should only remove the /proc/mtrr write permissions with
 > CONFIG_PAT. We need to deprecate it for a while before that...
 > Ingo, can you remove this PAT MTRR exclusion.

The removal of write-permission also needs to be decided at runtime rather than
compile time, or we screw over the "doesn't support PAT" CPUs in distro kernels.

	Dave

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