linux-kernel - Re: [tip:x86/urgent] x86, efi: Delete efi_ioremap() and fix CONFIG_X86

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Message-ID: <1331208578.3539.79.camel@mfleming-mobl1.ger.corp.intel.com>
Date:	Thu, 08 Mar 2012 12:09:38 +0000
From:	Matt Fleming <matt.fleming@...el.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...nel.org>, mingo@...hat.com,
	mjg@...hat.com, linux-kernel@...r.kernel.org, keithp@...thp.com,
	rui.zhang@...el.com, huang.ying.caritas@...il.com,
	stable@...r.kernel.org, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86, efi: Delete efi_ioremap() and fix
 CONFIG_X86_32 oops

On Wed, 2012-03-07 at 10:14 -0800, Yinghai Lu wrote:
> > +
> > +               if (end <= max_low_pfn << PAGE_SHIFT)
> > +                       max_low_pfn_mapped = last_pfn_mapped;
> 
> those two line could be dropped if you have
>             last_pfn_mapped = 1<<(20 - 12);
> before the loop

When you say "dropped" do you mean "not executed" or "deleted because
they are unnecessary"?

> Also you can not use  max_low_pfn here...

Why not? Please explain.

> you need to update e820_end_pfn to search max pfn for several types like
> > +               case E820_RAM:
> > +               case E820_RESERVED_EFI:
> > +               case E820_ACPI:
> > +               case E820_NVS:

Yeah, that's a good point. I'll make that change.

> but my question is:
> is there any system that will put EFI runtime, or ACPI or NVS above
> 4G? is that legal?

Matthew already answered this. I think it's entirely possible that EFI
runtime regions can reside above 4G.

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