From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v2 08/20] x86, ACPI: Find acpi tables in initrd early
 from head_32.S/head64.c
Date: Thu, 04 Apr 2013 13:25:37 -0700
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To: Pekka Enberg <penberg@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>, Tejun Heo <tj@kernel.org>, Thomas Renninger <trenn@suse.de>, Tang Chen <tangchen@cn.fujitsu.com>, linux-kernel@vger.kernel.org, Jacob Shin <jacob.shin@amd.com>, "Rafael J. Wysocki" <rjw@sisk.pl>, linux-acpi@vger.kernel.org

On 03/10/2013 03:25 AM, Pekka Enberg wrote:
> 
> What is preventing us from making the 64-bit variant also work in flat
> mode to make the code consistent and not hiding the differences under
> the rug? What am I missing here?
> 

There is no such thing as "flat mode" in 64-bit mode.  We use a #PF
handler to emulate it, but we add the normal kernel offset when doing so.

In the 32-bit case the problem is that the kernel offset is not
available while in linear mode.  It *could* be created using segment
bases, but that would break Xen, I'm pretty sure, and possibly some
other too-clever environments.

	-hpa