linux-kernel - Re: [RFC PATCH 0/4] EFI boot stub memory map fix

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Date:	Mon, 19 Aug 2013 15:09:39 -0600
From:	Linn Crosetto <linn@...com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Matt Fleming <matt.fleming@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Pekka Enberg <penberg@...nel.org>,
	Jacob Shin <jacob.shin@....com>, linux-efi@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/4] EFI boot stub memory map fix

On Mon, Aug 19, 2013 at 01:47:41PM -0700, Yinghai Lu wrote:
> On Mon, Aug 19, 2013 at 1:06 PM, H. Peter Anvin <hpa@...or.com> wrote:
> > I would strongly disagree that option 2 is the cleaner solution.
> 
> Agreed.
> 
> >
> > Linn Crosetto <linn@...com> wrote:
> >>I realize the EFI stub for ARM patches are in flight,
> >>
> >>https://lkml.org/lkml/2013/8/9/554
> >>
> >>and overlap with some of the files but I wanted to send these out for
> >>comment.
> >>
> >>This series fixes a problem with EFI memory maps larger than 128
> >>entries when
> >>booting using the EFI boot stub, which results in overflowing the
> >>e820_map in
> >>boot_params and an eventual halt when checking the map size in
> >>sanitize_e820_map().
> >>
> >>The fix implemented is to add the EFI memory map from setup_arch() via
> >>a
> >>memory_setup hook.
> >>
> >>Two options were considered:
> >>
> >> 1. Use the SETUP_E820_EXT setup_data type to add the extra entries.
> >>
> >>2. Create a memory_setup function to be enabled when the EFI memory map
> >>is
> >>    needed.
> >>
> >>Option 2 appeared to be the cleaner solution, reducing duplication with
> >>existing code, given a reasonable mechanism for determining when to
> >>replace the default memory_setup function.
> 
> If boot_loader could create setup_data with SETUP_E820_EXT,
> efi_stub should go that path too.
> We should not add another path.

My consideration was in leveraging do_add_efi_memmap(), which duplicates what is
done with the map in exit_boot(), and can already be called via the
"add_efi_memmap" parameter. One complication with SETUP_E820_EXT is in
determining the size needed, since a call to allocate_pool will change the
memory map. 

I will send another version which uses SETUP_E820_EXT.

Thanks,
Linn
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