linux-kernel - Re: [PATCH 2/2] efi: Distinguish between "remaining space" and actually used space

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Date:	Wed, 3 Apr 2013 17:20:30 +0000
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	Matt Fleming <matt@...sole-pimps.org>
CC:	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	"ben@...adent.org.uk" <ben@...adent.org.uk>,
	"jwboyer@...hat.com" <jwboyer@...hat.com>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"seth.forshee@...onical.com" <seth.forshee@...onical.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 2/2] efi: Distinguish between "remaining space" and
 actually used space

On Wed, 2013-04-03 at 18:12 +0100, Matt Fleming wrote:

> The solution you're proposing has the same downsides as 3) - we risk
> having to tweak things either way. The difference is that in the case of
> 3) the tweaking is adding entries to the whitelist, whereas tweaking
> your solution has more chance of introducing further unwanted
> regressions because you'd be tweaking an algorithm, an algorithm that
> relies on the internal implementation of the variable storage code.

We *risk* having to tweak things, and we fail on the side of safety. 

> > Dealing with firmware is hard. This fixes (1) without leaving us with
> > (2), which seems like a net win.
> 
> I'm not convinced that implementing 3) would inevitably lead to 2),
> provided that we apply a bit of common sense when adding entries. I'm
> not advocating some kind of flag day where we add umpteen machines to
> the whitelist.
> 
> For reference, I just pushed two patches to the 'whitelist' branch at,
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi.git
> 
> which should hopefully illustrate the kind of thing that I'm talking about.

I don't think that works. People are complaining that we broke some
Thinkpads as well, but we also have reports that Thinkpads can be
bricked if we use too much space.

-- 
Matthew Garrett | mjg59@...f.ucam.org