Re: [BUG] x86 kenel won't boot under Virtual PC

From: Linus Torvalds <torvalds@linux-foundation.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>,
	linux@sandersweb.net, linux-kernel@vger.kernel.org,
	the arch/x86 maintainers <x86@kernel.org>,
	Andi Kleen <andi-suse@firstfloor.org>
Subject: Re: [BUG] x86 kenel won't boot under Virtual PC
Date: Mon, 8 Sep 2008 09:20:06 -0700 (PDT)	[thread overview]
Message-ID: <alpine.LFD.1.10.0809080916550.3117@nehalem.linux-foundation.org> (raw)
In-Reply-To: <48C54F1B.8040604@zytor.com>

On Mon, 8 Sep 2008, H. Peter Anvin wrote:
> 
> And yes, it should be the default.  The patch I have makes it
> "default y" as well as change the help text.

It sounds like it shouldn't be a default at all, it should just _always_ 
be on, if there really are gcc's that care that much. Most of our 
optimizations have historically really been about _optimizing_, not about 
"it won't work", even if we have had exceptions (but as mentioned, I think 
those exceptions have been way more imporant than NOPL).

> Would it make you happier if this option was forced enabled unless
> CONFIG_EMBEDDED was on?

Yes, putting it behind EMBEDDED will certainly fix the issue. Anybody who 
actually enables EMBEDDED and does all his choices by hand should no 
longer expect to not have to know _exactly_ what he is doing.

So if it's behind EMBEDDED, and defaults to "on", then I have no problem 
with changing the help text to say "If you do this, we'll statically do 
things that really _require_ you to have a CPU that looks _exactly_ like 
the CPU you claimed".

		Linus