From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Mikael Petterson <mikpe@it.uu.se>,
Eric Biederman <ebiederm@xmission.com>
Subject: Re: [GIT PULL] x86 setup: correct booting on 486DX4
Date: Sun, 04 Nov 2007 15:27:58 -0800 [thread overview]
Message-ID: <472E557E.3010903@goop.org> (raw)
In-Reply-To: <alpine.LFD.0.999.0711041512530.15101@woody.linux-foundation.org>
Linus Torvalds wrote:
> I'm not entirely sure that it needs to be a long-jump, btw. I think any
> regular branch is sufficient. You obviously *do* need to make the long
> jump later (to reload %cs in protected mode), but I'm not sure it's needed
> in that place. I forget the exact rules (but they definitely were
> documented).
Yes, it says it needs to be a far jmp or call (and if you enabled paging
in the cr0 load, you need to identity-map the branch target). Having
successfully broken the rules for a long time so far, maybe we can get
away with still cutting corners... but it doesn't seem particularly
worthwhile since we've been caught once.
J
next prev parent reply other threads:[~2007-11-04 23:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200711042259.lA4Mxa0n025210@tazenda.hos.anvin.org>
2007-11-04 23:17 ` [GIT PULL] x86 setup: correct booting on 486DX4 Linus Torvalds
2007-11-04 23:25 ` Linus Torvalds
2007-11-04 23:36 ` H. Peter Anvin
2007-11-04 23:26 ` H. Peter Anvin
2007-11-04 23:59 ` Linus Torvalds
2007-11-05 0:02 ` H. Peter Anvin
2007-11-05 0:12 ` H. Peter Anvin
2007-11-05 0:43 ` Eric W. Biederman
2007-11-05 1:10 ` Linus Torvalds
2007-11-04 23:27 ` Jeremy Fitzhardinge [this message]
2007-11-04 22:57 H. Peter Anvin
2007-11-05 0:14 ` Eric W. Biederman
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