linux-kernel - Re: [PATCH] Remove warning in efi_enter_virtual

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Message-ID: <517053EF.2030900@zytor.com>
Date:	Thu, 18 Apr 2013 13:13:35 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Darren Hart <darren.hart@...el.com>
CC:	Matthew Garrett <matthew.garrett@...ula.com>,
	Matt Fleming <matt@...sole-pimps.org>,
	Josh Triplett <josh@...htriplett.org>,
	"Bryan O'Donoghue" <bryan.odonoghue.lkml@...us-software.ie>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Josh Boyer <jwboyer@...hat.com>
Subject: Re: [PATCH] Remove warning in efi_enter_virtual_mode

On 04/18/2013 01:11 PM, Darren Hart wrote:
>>
>> I would expect that if there are any 32-bit UEFI systems that ship with
>> BGRT support (and Darren makes it sound like that's a possibility),
>> there's a realistic chance of the BGRT ending up allocated above the
>> highmem barrier.
> 
> I can certainly ensure we sit below that barrier on the MinnowBoard. We
> can also speak with the Intel UEFI firmware development teams to see
> about making that a requirement. I don't know if we'll be successful,
> but Matt, Peter, and I have recently coaxed some changes of that nature in.
> 

No, that is the wrong approach.  The HIGHMEM barrier is a Linux kernel
construct and isn't even guaranteed to be the same from one boot *of the
same kernel* to another.  The value 896M is merely the default, but it
can be affected by both compile time and command line options.

	-hpa

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