linux-kernel - Re: [RFC PATCH 1/3] Replace paravirt_probe with "platform type" boot header field

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Message-ID: <463B69AB.2030706@zytor.com>
Date:	Fri, 04 May 2007 10:13:15 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Rusty Russell <rusty@...tcorp.com.au>, Andi Kleen <ak@...e.de>,
	Chris Wright <chrisw@...s-sol.org>,
	Jeremy Fitzhardinge <jeremy@...p.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 1/3] Replace paravirt_probe with "platform type" boot
 header field

Eric W. Biederman wrote:
> "H. Peter Anvin" <hpa@...or.com> writes:
> 
>> Eric W. Biederman wrote:
>>> Unlikely.  Unless we expect that this offset will come in non-zero.
>>>
>> You might have to worry about that.  Historically, the "zero-page" was
>> really just the setup code overwritten, and it's still true for a big
>> chunk of it.
>>
>> One of the major changes in my setup code rewrite is to start out with
>> an all-zero chunk of memory for this.
> 
> Well as long as we are in sync with setup.S we are fine.  The issue
> is people generating the real-mode data from scratch, when using the
> 32bit entry point.

Point.  I'd like that interface to specify that any undefined fields
should be zero, or we have a hopeless situation on our hands.

By the way, see the following for the structure definition; prepare to barf:

http://git.kernel.org/?p=linux/kernel/git/hpa/linux-2.6-newsetup.git;a=blob;f=arch/i386/boot/boot.h;h=41a16f96ac3476cbd969aabe5e6a792ffe8c64a0;hb=HEAD

[I intend to move this into include/asm-i386/boot.h, but haven't gotten
that far yet.  I just yesterday got the code booting on both i386 and
x86-64, but haven't committed all the include/asm-* mods that went a
long with that yet.  I'm also waiting for a Kbuild fix so that the boot
directory can be shared between i386 and x86-64 without requiring a
symlink in the source tarball.]

	-hpa
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