linux-kernel - Re: [RFC PATCH 3/3] boot bzImages under paravirt

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Message-ID: <463B5B90.20308@goop.org>
Date:	Fri, 04 May 2007 09:13:04 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Rusty Russell <rusty@...tcorp.com.au>, Andi Kleen <ak@...e.de>,
	Chris Wright <chrisw@...s-sol.org>,
	Zachary Amsden <zach@...are.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 3/3] boot bzImages under paravirt

H. Peter Anvin wrote:
> In 32-bit mode?  Surely you're joking, Mr. Feynman!
>   

Right, yes.

> What's worse, reloading segments here might be highly unsafe, if the
> memory previously occupied by the GDT has been overwritten.  Keep in
> mind the GDT is touched on a segment *load*, not on a segment *access*;
> in areas such as booting that can be a huge difference.
>   

Yep, suits me.  I'm happy for the code to assume that at least %cs and
%ds are sane; I guess %ss too.  We could copy %ds into %[efg]s if we
want to be sure (since I could imagine a bootloader leaving them in a
less defined state).

But if the gdt could be missing altogether, then, yes, we should not
touch them at all.

    J
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