linux-kernel - Re: [PATCH] Fix i486 suspend to disk CR4 oops

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Message-ID: <20080818125803.GC17528@spacedout.fries.net>
Date:	Mon, 18 Aug 2008 07:58:03 -0500
From:	David Fries <david@...es.net>
To:	"Maciej W. Rozycki" <macro@...ux-mips.org>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Pavel Machek <pavel@....cz>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH] Fix i486 suspend to disk CR4 oops

On Mon, Aug 18, 2008 at 05:14:50AM +0100, Maciej W. Rozycki wrote:
> On Sun, 17 Aug 2008, David Fries wrote:
> > +	/* cr4 was introduced in the Pentium CPU */
> 
>  NACK.  Later i486 chips do have CR4 -- for PSE, VME, etc. (the set of
> features varies across the line).  Use a fixup as elsewhere or something.
> 
>   Maciej

That's what I get for reading the Intel instruction set reference,
"The CR4 register was added to the Intel Architecture beginning with
the Pentium processor."

Ingo Molnar, thanks, I'll try the read_cr4_safe() version tonight (the
computer is in the trunk of my car and I'm about ready to head to
work).

In light of the above, how about updating the comments
-       /* cr4 was introduced in the Pentium CPU */
-       jecxz   1f      # cr4 Pentium and higher, skip if zero
+       /* cr4 not in i386 only some i486, skip if zero */
+       jecxz   1f      # cr4 not in i386 only some i486, skip if zero

I'm not being bit by arch/x86/kernel/relocate_kernel_32.S, but it is
using cr4.  Should that be fixed up as well?

-- 
David Fries <david@...es.net>
http://fries.net/~david/ (PGP encryption key available)
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