linux-kernel - Re: [regression, bisected] x86: efi: Pass boot services variable info to runtime code

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Date:	Sat, 1 Jun 2013 01:30:39 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Russ Anderson <rja@....com>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	joeyli <jlee@...e.com>, Matt Fleming <matt@...sole-pimps.org>,
	matt.fleming@...el.com, linux-efi@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [regression, bisected] x86: efi: Pass boot services variable
 info to runtime code

On Fri, 31 May 2013, Russ Anderson wrote:

> OK.  I get nvram looks full due to lack of garbage collection
> on some systems.  Does QueryVariableInfo (at runtime) tell you
> it is full?  Is the problem that it says it is full when it
> is not, or does not tell you it is full when it is?

We are trying to count the size occupied by existing UEFI variables. 
QueryVariableInfo() called from runtime environment doesn't give a full 
picture, as it doesn't provide information about boot-only variables.

Hence the patch.

> > up the size of the variables ourselves, but that only gives us the value 
> > for runtime-visible variables. We also need to know how much space is 
> > used by variables that are only visible during boot,
> 
> Is it valid to assume that only the kernel writes to nvram at
> runtime?  

Well, mostly yes. But if the kernel doesn't know what the initial state 
is, it can't count the size properly.

> > > Which means the previous patch(es) that caused the bricking should
> > > get pulled, too.
> > 
> > There are no patches that cause the bricking.
> 
> I thought that was the problem you were trying to avoid.

The problem that needs to be avoided is machines turning into bricks if 
EFI storage nvram is getting full.

-- 
Jiri Kosina
SUSE Labs
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