linux-kernel - Re: [PATCH 0/3] Fix ACPI BGRT support for images located in EFI boot services memory

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Date:	Tue, 04 Sep 2012 15:27:20 +0100
From:	Matt Fleming <matt.fleming@...el.com>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Len Brown <lenb@...nel.org>, Olof Johansson <olof@...om.net>,
	Matthew Garrett <mjg@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jim Cromie <jim.cromie@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Pawel Moll <pawel.moll@....com>, linux-acpi@...r.kernel.org,
	linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH 0/3] Fix ACPI BGRT support for images located in EFI
 boot services memory

On Thu, 2012-08-30 at 14:28 -0700, Josh Triplett wrote:
> The ACPI BGRT lets the OS access the BIOS logo image and its position on the
> screen at boot time, allowing it to maintain that image on the screen until
> ready to display something else, making boot more seamless.  This series fixes
> support for accessing the boot logo image via the BGRT when the BIOS stores it
> in EFI boot services memory, as recommended by the ACPI 5.0 spec.  Linux needs
> to copy the image out of boot services memory before reclaiming boot services
> memory.
> 
> The first patch refactors EFI initialization to defer freeing boot services
> memory until later in the boot process, after we have ACPI available.  The
> second patch adds a helper function to look up existing EFI boot services
> mappings, to avoid re-mapping them.  The third patch moves BGRT initialization
> to before the reclamation of boot services memory, copies the logo at that
> point, and reworks the existing BGRT driver to use that existing copy.

Since we always end up doing a copy anyway, is there no way we could
just copy the boot logo *without* deferring freeing the boot services
code, e.g. move the copy before we do SetVirtualAddressMap()? I wouldn't
be surprised if some implementations got really cranky if we accessed
boot services data after we installed a new virtual memory map.

Besides, if we can avoid moving the efi_free_boot_services() call we can
avoid littering init/main.c with more #ifdef CONFIG_X86 blocks.

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