From: Ian Campbell <ijc@hellion.org.uk>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: huang ying <huang.ying.caritas@gmail.com>,
       "Huang, Ying" <ying.huang@intel.com>, akpm@linux-foundation.org,
       Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
       Andi Kleen <ak@suse.de>, linux-kernel@vger.kernel.org,
       Jeremy Fitzhardinge <jeremy@goop.org>
In-Reply-To: <4790BD90.9060303@zytor.com>
References: <1200375906.3505.30.camel@caritas-dev.intel.com>
	 <1200646105.17230.28.camel@cthulhu.hellion.org.uk>
	 <851fc09e0801180654u6957f966g47c7629db6d4b2b0@mail.gmail.com>
	 <4790BD90.9060303@zytor.com>
Content-Type: text/plain
Date: Fri, 18 Jan 2008 15:54:25 +0000
Message-Id: <1200671665.9891.45.camel@localhost.localdomain>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: Re: [PATCH -mm 1/3] i386 boot: replace boot_ioremap with enhanced
	bt_ioremap - enhance bt_ioremap
Sender: linux-kernel-owner@vger.kernel.org
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On Fri, 2008-01-18 at 09:54 -0500, H. Peter Anvin wrote:
> huang ying wrote:
> > 
> > If CONFIG_X86_PAE is defined, the set_pte, clear_pte etc will operate
> > 3-level page tables, while on i386, the early page table is always
> > 2-level, so set_pte, clear_pte etc functions can not be used here. The
> > boot_ioremap use a trick to deal with this problem. The CONFIG_X86_PAE
> > is undefined in arch/x86/mm/boot_ioremap_32.c unconditionally, so the
> > 2-level page table handling function is always used.
> > 
> > Is the method used by boot_ioremap better for Xen?
> > 
> 
> Eric Biederman had a patchset that makes a PAE kernel use PAE page 
> tables from the start.  That is really The Right Thing[TM].

That's much saner than dup'ing up the early ioremap stuff to support
both PAE and non-PAE at runtime, which is about the only idea I've got
for fixing this right now...

I think I'll just back out the early_ioremap patches locally for now and
wait for Eric's patches which should cause the fix for this issue to
just fall out in the wash.

Ian.
-- 
Ian Campbell
Current Noise: Mistress - Mistress

Everything should be built top-down, except this time.

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