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From: "John S. Dyson" <toor@dyson.iquest.net>
Message-Id: <199612221724.MAA07051@dyson.iquest.net>
Subject: Re: P6 problem idea
To: phk@freebsd.org
Date: Sun, 22 Dec 1996 12:24:35 -0500 (EST)
Cc: smp@freebsd.org
In-Reply-To: <24900.851245819@critter.tfs.com> from "Poul-Henning Kamp" at Dec 22, 96 10:10:19 am
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> 
> 
> John Dyson has enabled the "Global" bit on some parts of the kernel.
> This makes the marked pages immune to TLB flushes.  Could this be the
> reason for the P6 Problems ?
> 
> I belive there is a bit in a control register that will enable/disable
> this, it's probably in locore.s somewhere.
> 
If you want to test that -- all you have to do is to disable the
setting of PG_G in locore and in pmap.  You can also optionally
turn off the capability (but you still need to disable all of the
PG_G bit setting) by not setting the CR4_PGE bit in cr4 also.

This *could* be the problem, because you need to do the single page
updates when the PG_G bit has been set (or there are more complex ways
of doing it also.)  The global update will just not work...  (Of course,
that is much of the purpose of the PG_G bit :-)).

John