linux-kernel - Re: [PATCH] efi/capsule: Make efi_capsule

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Date:	Thu, 5 May 2016 15:55:26 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	"Kweh, Hock Leong" <hock.leong.kweh@...el.com>,
	"Bryan O'Donoghue" <pure.logic@...us-software.ie>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	joeyli <jlee@...e.com>, Borislav Petkov <bp@...en8.de>,
	"Ong, Boon Leong" <boon.leong.ong@...el.com>,
	"Ong, Kean Chai" <kean.chai.ong@...el.com>
Subject: Re: [PATCH] efi/capsule: Make efi_capsule_pending() lockless

On Thu, 5 May 2016 15:36:43 +0100
Matt Fleming <matt@...eblueprint.co.uk> wrote:

> On Thu, 05 May, at 02:27:16PM, Kweh, Hock Leong wrote:
> > 
> > If not mistaken, the EFI firmware will not update a partially uploaded binary due to checksum error.
> > User is required to re-update the efi capsule again on the next boot up.  
> 
> Ah, so the capsule is only processed by the firmware after rebooting?
> That makes sense and alleviates my concerns about rebooting while in
> the middle of efi_capsule_update().

Yes - and in many cases the actions the firmware capsule update does are
done in a manner which once you exit the firmware cannot be done by the
OS. It acts as a way to communicate a block of (typically signed)
firmware to more hardware priviliged boot firmware.

Alan