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

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Message-ID: <20130531100606.GC30394@gmail.com>
Date:	Fri, 31 May 2013 12:06:06 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Russ Anderson <rja@....com>
Cc:	Matthew Garrett <matthew.garrett@...ula.com>,
	joeyli <jlee@...e.com>, Jiri Kosina <jkosina@...e.cz>,
	Matt Fleming <matt@...sole-pimps.org>,
	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [regression, bisected] x86: efi: Pass boot services variable
 info to runtime code


* Russ Anderson <rja@....com> wrote:

> On Thu, May 30, 2013 at 10:32:09PM +0000, Matthew Garrett wrote:
> > On Thu, 2013-05-30 at 17:28 -0500, Russ Anderson wrote:
> > > On Thu, May 30, 2013 at 10:21:53PM +0000, Matthew Garrett wrote:
> > > > On Thu, 2013-05-30 at 17:17 -0500, Russ Anderson wrote:
> > > > 
> > > > > That's a great idea.  This patch moves the QueryVariableInfo()
> > > > > call from bootime to runtime, in efi_late_init().  The attached
> > > > > patch is consistent with the UEFI spec and avoids the problem.
> > > > 
> > > > No, that defeats the entire point of the original patch.
> > > 
> > > How so?  It is still calling QueryVariableInfo()
> > > before the data is used.
> > 
> > We want to know how much space is used by variables that aren't visible
> > at runtime.
> 
> We want to boot.  We could boot up through 3.9-rc7.
> 
> Knowing how much space is used by variables that aren't
> visible at runtime it moot if you can't boot.

Exactly - fixing a boot regression is _WAY_ more important than pretty 
much any other concern.

and the boot breakage is not limited to UV systems - the thread mentioned 
a couple of other systems as well.

So it's an absolute no-brainer that this change should be reverted or 
fixed via your patch.

Once a safer mechanism is implemented to call QueryVariableInfo() earlier 
(Boris's patches?) the change can be reintroduced.

Thanks,

	Ingo
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