linux-kernel - Re: Revert commit 5dcd14ecd4 - breaks EFI boot with SLES11 elilo.efi

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Message-ID: <51377C3A.3030301@zytor.com>
Date:	Wed, 06 Mar 2013 09:26:18 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Josh Boyer <jwboyer@...il.com>
CC:	Yinghai Lu <yinghai@...nel.org>, Robin Holt <holt@....com>,
	hpa@....com, linux-kernel@...r.kernel.org, pjones@...hat.com
Subject: Re: Revert commit 5dcd14ecd4 - breaks EFI boot with SLES11 elilo.efi

On 03/06/2013 08:53 AM, Josh Boyer wrote:
> 
> I don't think this is limited to elilo.  I have a UEFI machine booting
> with grub2 that also fails to boot because of this patch.  I was in the
> middle of bisecting when I found this thread and if I revert 5dcd14ecd4
> the machine boots again.  Put that commit back in and it doesn't.  We've
> had three other reports in Fedora of similar cases.
> 
> I discussed this with Peter Jones this morning.  He was looking into what
> grub2 does for boot_params and it seems to be read-modify-write instead
> of clearing the whole thing.  (CC'd Peter now.)
> 
> The patch for elilo probably works, but if grub2 is hitting this then I'm
> curious if most bootloaders will.  I'll finish my bisect just to be extra
> sure, but something probably needs to be done in a more generic fashion
> here.
> 

Come to think about it...

The EFI field actually has a magic, unless just about all the rest of
them, so clearing it is probabilistically redundant; in other words we
almost certainly should exclude it from the clearing, unconditionally.

Does the "elilo" patch made unconditional work for you?

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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