From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Mikael Pettersson <mikpe@it.uu.se>
Cc: hpa@zytor.com, linux-kernel@vger.kernel.org, mingo@redhat.com,
tglx@linutronix.de
Subject: Re: [PATCH] fix i486 boot failure due to stale %ds
Date: Sun, 04 Nov 2007 15:07:49 -0800 [thread overview]
Message-ID: <472E50C5.5020201@goop.org> (raw)
In-Reply-To: <200711042158.lA4Lwv9S014628@harpo.it.uu.se>
Mikael Pettersson wrote:
> On Sun, 04 Nov 2007 11:41:58 -0800, H. Peter Anvin wrote:
>
>> Mikael Pettersson wrote:
>>
>>> First patch didn't build. Second patch builds and boots Ok.
>>>
>>> So this means the 486 DX4 has a buggy mov to %cr0?
>>>
>>>
>> Apparently.
>>
>
> 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...
J
next prev parent reply other threads:[~2007-11-04 23:08 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 [this message]
2007-11-04 23:12 ` H. Peter Anvin
2007-11-04 23:50 ` H. Peter Anvin
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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