linux-kernel - Re: ACPI early ioremap problems

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Date:	Sat, 19 Jan 2008 19:45:43 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	venkatesh.pallipadi@...el.com, suresh.b.siddha@...el.com,
	tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: ACPI early ioremap problems


* Andi Kleen <andi@...stfloor.org> wrote:

> On Sat, Jan 19, 2008 at 04:30:55PM +0100, Ingo Molnar wrote:
> > > > that case it's a 64-bit early_ioremap() bug that we want to find 
> > > > even if ACPI didnt use early_ioremap().
> > > > 
> > > > and this all runs before zap_low_mappings(), right?
> > > 
> > > No after. Since some time x86-64 does the equivalent of z_l_m() in 
> > > head64(); this means before start_kernel and definitely before 
> > > setup_arch which sets up ACPI.
> > 
> > that would mean early_ioremap() should switch to ioremap() after that 
> > point. Could you try that, does it resolve the failure you are seeing? 
> 
> ioremap() does alloc_page and that won't work before paging_init(). 
> Early ACPI scan is before paging_init() because paging_init() needs 
> node discovery at at least; which requires some ACPI tables.

hm, so are you saying that on 64-bit there's in essence no usable 
ioremap facility between zap_low_mappings() and paging_init()? 
(early_ioremap() is not usable anymore, and ioremap() is not yet 
usable.) I guess we'll have to pick up the 32-bit early_ioremap() code 
for 64-bit as well.

	Ingo
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