From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jan Beulich <jbeulich@novell.com>
Cc: linux@sandersweb.net, Ingo Molnar <mingo@elte.hu>,
Andi Kleen <andi-suse@firstfloor.org>,
Arjan van de Ven <arjan@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [BUG] x86 kenel won't boot under Virtual PC
Date: Fri, 5 Sep 2008 09:39:38 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.1.10.0809050931340.3117@nehalem.linux-foundation.org> (raw)
In-Reply-To: <48C17754.76E4.0078.0@novell.com>
On Fri, 5 Sep 2008, Jan Beulich wrote:
>
> I disagree here: If I configure a 686+ kernel, I expect these NOPs to be
> that way (and to work). If you want to run on something that's not
> compliant, you just shouldn't configure your kernel that way.
Well, if you actually do a
git grep 'ASM_NOP[0-9]'
you'll find that just the _definitions_ of those things are the bulk of it
BY FAR, and that there doesn't seem to be a single user that cares even
remotely about performance.
So I actually think that the whole thing is a waste of time. We should
probably
- pick a single set of NOP's per 32-bit/64-bit (since the good nops in
32-bit aren't 64-bit instructions at all, so we do want different nops
depending on _that_)
The whole static choice by microarchitecture is pure garbage.
- Probably also just declare that those default nops are single
instructions, just so that we never even have to think about it from a
dynamic replacement angle.
Look at the uses again, and realize that it really is just pure garbage
to have this kind of complex and subtle stuff going on.
- Move the optimized nop definitions (K7_NOPx etc) to the only place that
cares - asm/x86/kernel/alternative.c. When we do things _dynamically_,
it can actually make sense to pick a nop more precisely, but for this
whole static thing it's just a pain.
IOW, if it actually _worked_ reasonably, I wouldn't care. But clearly it
doesn't. And once it's not working reasonably, it should be fixed.
Linus
next prev parent reply other threads:[~2008-09-05 16:40 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-31 18:22 [BUG] x86 kenel won't boot under Virtual PC David Sanders
2008-08-31 18:47 ` Linus Torvalds
2008-08-31 19:27 ` Arjan van de Ven
2008-08-31 19:39 ` Linus Torvalds
2008-09-05 15:38 ` David Sanders
2008-09-05 16:15 ` Jan Beulich
2008-09-05 16:39 ` Linus Torvalds [this message]
2008-09-05 18:43 ` Ingo Molnar
2008-09-05 20:06 ` H. Peter Anvin
2008-09-05 19:08 ` Jeremy Fitzhardinge
2008-09-05 20:12 ` H. Peter Anvin
2008-09-05 16:30 ` Linus Torvalds
2008-09-05 17:55 ` Andi Kleen
2008-08-31 20:03 ` David Sanders
2008-09-01 20:23 ` David Sanders
2008-09-01 22:22 ` Linus Torvalds
2008-09-02 12:08 ` David Sanders
2008-09-02 18:12 ` Linus Torvalds
2008-09-02 18:44 ` David Sanders
2008-09-03 11:09 ` Peter Zijlstra
2008-09-03 11:20 ` David Sanders
[not found] ` <48C1C156.9080003@zytor.com>
2008-09-07 20:07 ` David Sanders
2008-09-07 23:22 ` David Sanders
2008-09-08 1:48 ` H. Peter Anvin
2008-09-08 2:49 ` David Sanders
2008-09-08 4:04 ` H. Peter Anvin
2008-09-08 9:42 ` Andi Kleen
2008-09-08 13:25 ` David Sanders
2008-09-08 15:09 ` Linus Torvalds
2008-09-08 15:23 ` Ingo Molnar
2008-09-08 15:36 ` H. Peter Anvin
2008-09-08 15:38 ` David Sanders
2008-09-08 15:38 ` H. Peter Anvin
2008-09-08 15:45 ` Andi Kleen
2008-09-08 15:43 ` H. Peter Anvin
2008-09-08 15:50 ` H. Peter Anvin
2008-09-08 15:50 ` Andi Kleen
2008-09-08 15:50 ` H. Peter Anvin
2008-09-08 15:57 ` Andi Kleen
2008-09-08 15:54 ` H. Peter Anvin
2008-09-08 16:07 ` Linus Torvalds
2008-09-08 16:13 ` H. Peter Anvin
2008-09-08 16:15 ` H. Peter Anvin
2008-09-08 16:26 ` David Sanders
2008-09-08 16:20 ` Linus Torvalds
2008-09-08 16:32 ` H. Peter Anvin
2008-09-08 17:02 ` Ingo Molnar
2008-09-08 16:34 ` david
2008-09-08 16:42 ` H. Peter Anvin
2008-09-08 18:51 ` david
2008-09-08 16:59 ` Linus Torvalds
2008-09-08 17:00 ` Andi Kleen
2008-09-08 17:04 ` Linus Torvalds
2008-09-08 17:08 ` H. Peter Anvin
2008-09-08 17:12 ` H. Peter Anvin
2008-09-08 17:41 ` Linus Torvalds
2008-09-08 17:38 ` Linus Torvalds
2008-09-08 17:59 ` H. Peter Anvin
2008-09-08 19:09 ` H. Peter Anvin
2008-09-08 22:42 ` Linus Torvalds
2008-09-08 17:18 ` Andi Kleen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.LFD.1.10.0809050931340.3117@nehalem.linux-foundation.org \
--to=torvalds@linux-foundation.org \
--cc=andi-suse@firstfloor.org \
--cc=arjan@infradead.org \
--cc=jbeulich@novell.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@sandersweb.net \
--cc=mingo@elte.hu \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).