linux-kernel - Re: [PATCH 2/4] efi: Capsule update support

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Message-ID: <20160321203159.GF11676@codeblueprint.co.uk>
Date:	Mon, 21 Mar 2016 20:31:59 +0000
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	joeyli <jlee@...e.com>,
	Kweh Hock Leong <hock.leong.kweh@...el.com>,
	Borislav Petkov <bp@...en8.de>,
	Mark Salter <msalter@...hat.com>,
	Peter Jones <pjones@...hat.com>,
	Bryan O'Donoghue <pure.logic@...us-software.ie>
Subject: Re: [PATCH 2/4] efi: Capsule update support

On Mon, 21 Mar, at 11:19:50AM, Ard Biesheuvel wrote:
> 
> How are capsules with the CAPSULE_FLAGS_INITIATE_RESET flag handled?
> The runtime service will never return in that case, so I suppose we
> need some explicit handling somewhere?

Good question. They're not handled in any special way with this patch
series, so the firmware will just initiate its own reset inside of
UpdateCapsule().

That's probably not what we want, because things like on-disk
consistency are not guaranteed if the machine spontaneously reboots
without assistance from the kernel.

The simplest thing to do is to refuse to pass such capsules to the
firmware, since it's likely not going to be a common use case. But
maybe that's overly restrictive.

Let me have a think about that one.