From: Jamie Lokier <jamie@shareable.org>
To: Coywolf Qi Hunt <coywolf@greatcn.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Re: BOOT_CS
Date: Mon, 23 Feb 2004 14:30:56 +0000 [thread overview]
Message-ID: <20040223143056.GC30321@mail.shareable.org> (raw)
In-Reply-To: <403984DD.4030108@greatcn.org>
Coywolf Qi Hunt wrote:
> >It's to flush the instruction prefetch queue: that's one of the side
> >effects of ljmp.
>
> Re-loading %cs and flushing prefetch queue are two different things.
Yes, they are.
> FYI, intel's example code located in STARTUP.ASM Listing arround line
> 180, chapter 9, IA-32 Intel Architecture Software Developer's Manual,
> Volume 3: System Programming Guide
Thanks.
> Please consider my patch for this issue.
I don't have the ability to look at that manual right now.
Your patch uses two instructions to flush the queue (push+ret) instead
of one (jmp or ljmp). Is that documented as reliable? I can easily
imagine an implementation which decodes one instruction after a mode
change predictably, but not two.
I doubt that it makes a difference - we're setting PG, not changing
the instruction format - but I'd like us to be sure it cannot fail on
things like 386s and 486s, and similar non-Intel chips.
-- Jamie
next prev parent reply other threads:[~2004-02-23 14:31 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-21 5:47 BOOT_CS H. Peter Anvin
2004-02-21 12:43 ` BOOT_CS Coywolf Qi Hunt
2004-02-21 16:32 ` BOOT_CS Jamie Lokier
2004-02-23 4:43 ` [PATCH] BOOT_CS Coywolf Qi Hunt
2004-02-23 14:30 ` Jamie Lokier [this message]
2004-02-23 15:24 ` Rene Herman
2004-02-24 3:11 ` [PATCH] Remove the extra jmp Coywolf Qi Hunt
2004-02-24 3:30 ` Brian Gerst
2004-02-24 10:10 ` Coywolf Qi Hunt
2004-02-22 15:13 ` BOOT_CS Eric W. Biederman
2004-02-22 19:47 ` BOOT_CS H. Peter Anvin
2004-02-22 22:05 ` BOOT_CS Eric W. Biederman
2004-02-23 10:27 ` Does Flushing the Queue after PG REALLY a Necessity? Coywolf Qi Hunt
2004-02-23 15:18 ` Philippe Elie
2004-02-24 2:36 ` Coywolf Qi Hunt
2004-02-24 3:10 ` H. Peter Anvin
2004-02-24 4:55 ` Randy.Dunlap
2004-02-24 9:17 ` Coywolf Qi Hunt
2004-02-24 11:21 ` Herbert Poetzl
2004-02-24 11:33 ` Coywolf Qi Hunt
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