From: "H. Peter Anvin" <hpa@zytor.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Mikael Pettersson <mikpe@it.uu.se>,
linux-kernel@vger.kernel.org, mingo@redhat.com,
tglx@linutronix.de,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] fix i486 boot failure due to stale %ds
Date: Sun, 04 Nov 2007 15:50:14 -0800 [thread overview]
Message-ID: <472E5AB6.40509@zytor.com> (raw)
In-Reply-To: <472E50C5.5020201@goop.org>
Jeremy Fitzhardinge wrote:
>> Maybe not. I had a look in Intel's SDM Vol3, and the
>> section "switching to protected mode" specifies that
>> a move to %cr0 that sets PE should immediately be
>> followed by a far jmp or call.
>
> Yes, that's what the spec says. I queried this a few months ago, but
> hpa used his convincing voice and said that in practice it isn't
> necessary; there are no known cpus which need this, and any that do
> would cause other things to break. But I guess now we have the
> counter-example...
Joy. Apparently the Intel documentation is actually self-inconsistent.
Section 9.9.1, page 9-17 does indeed have the "far jump or call"
injunction, whereas the sample code in section 9.10.1, page 9-27, line
180 does a near jump!
-hpa
next prev parent reply other threads:[~2007-11-04 23:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-04 21:58 [PATCH] fix i486 boot failure due to stale %ds Mikael Pettersson
2007-11-04 22:20 ` H. Peter Anvin
2007-11-04 23:05 ` Andi Kleen
2007-11-04 23:07 ` Jeremy Fitzhardinge
2007-11-04 23:12 ` H. Peter Anvin
2007-11-04 23:50 ` H. Peter Anvin [this message]
2007-11-05 0:15 ` Linus Torvalds
2007-11-05 0:23 ` Linus Torvalds
2007-11-04 23:51 ` H. Peter Anvin
-- strict thread matches above, loose matches on Subject: below --
2007-11-05 1:18 Mikael Pettersson
2007-11-04 19:38 Mikael Pettersson
2007-11-04 19:41 ` H. Peter Anvin
2007-11-04 16:44 Mikael Pettersson
2007-11-04 18:29 ` H. Peter Anvin
2007-11-04 19:00 ` H. Peter Anvin
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