linux-kernel - Re: [tip:efi/core] efibc: Add EFI Bootloader Control module

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Date:	Sat, 30 Apr 2016 21:01:24 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	"Compostella, Jeremy" <jeremy.compostella@...el.com>
Cc:	Ingo Molnar <mingo@...nel.org>, stefan.stanacar@...el.com,
	peterz@...radead.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, hpa@...or.com, bp@...en8.de,
	ard.biesheuvel@...aro.org, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:efi/core] efibc: Add EFI Bootloader Control module

On Sat, 30 Apr, at 10:33:32AM, Jeremy Compostella wrote:
> Ingo Molnar <mingo@...nel.org> writes:
> >
> > Hm, can reboot notifiers do non-atomic allocations?
> The reboot notifier chain is a blocking notifier chain. AFAIK, it
> allows non-atomic allocation, right ?
 
I would assume so, yes.

> > Why is efivar_entry so huge?
> efivar_entry structure include two "big" arrays of 1024 bytes each for
> the EFI variable name and data.

Yeah. This is partially historical in that the EFI variable code has
always had these arrays.

But it's also that if you're dealing with EFI variables you always
want someplace to cache the data and name, so no one has ever proposed
to split out the data/name from struct efivar_entry.

We've never put them on the stack before either ;)