linux-kernel - Re: [BUG]: DELL XPS 8500 become a brick after fill too many entries to nvram.

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Date:	Mon, 11 Nov 2013 20:38:31 +0800
From:	Madper Xie <cxie@...hat.com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Madper Xie <cxie@...hat.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi\@vger.kernel.org" <linux-efi@...r.kernel.org>,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: [BUG]: DELL XPS 8500 become a brick after fill too many entries to nvram.


matt@...sole-pimps.org writes:

> On Mon, 11 Nov, at 02:15:22PM, Madper Xie wrote:
>> Howdy all,
>>   For now we ensure at least ~5kb free space. But my dell xps still
>>   become a brick after I add too many entries to my nvram. So maybe 5kb
>>   is not safe enough. and 5kb is just aginst Samsung's laptop.
>>   So should we enlarge EFI_MIN_RESERVE?
>
> Urgh.............
>
> Thanks for the report. Could you provide some more details?
>
>  - Is your machine definitely bricked?
Yes, pretty sure. After I press power button, the screen shows "DELL"
and hangs. I can't step into any configure interface and the keyboard is
dead. (NumLock led on, and I can't turn it off.) Of course my kernel
won't be loaded. The only way to fix it is change the jump line which is
on the motherboard.
>  - Exactly which Dell machine is this?
Dell XPS 8500. Link here: http://www.dell.com/us/p/xps-8500/pd
>  - What were you doing to cause your machine to not boot? Using
>    efibootmgr?
I already have more than 100 pstore entries and backend is
efi. But yes, efibootmgr trigger this accident.
>  - Please send your .config
Attached.
Download attachment "config" of type "application/octet-stream" (102309 bytes)


>  - Have you reported this to any BIOS engineers to confirm the cause of
>    the bricking?
Not really. The girl who answer my phone from DELL side doesn't really
know what NVRAM is... But I have reproduced this issue many times. (for
finding the threshold.) I simply occupy nvrams by:
for i in `seq 20`; do head -c20480 /dev/urandom | efibootmgr --quiet --create --append-binary-args - ; done
>  - Have you got a dmesg from the machine before it broke?
No. But with a diagnostic kernel(without change the behavior of
efi. Simply print total size and remain size when I write something to
nvram. Provided by Lenny), I got following output:

[  254.811220] EFI: efi_query_variable_store, total size=131072., remain=22968.
[  254.978133] EFI: efi_query_variable_store, total size=131072., remain=21924.
[  255.016127] EFI: efi_query_variable_store, total size=131072., remain=21758.
[  255.183644] EFI: efi_query_variable_store, total size=131072., remain=20714.
[  255.209139] EFI: efi_query_variable_store, total size=131072., remain=20546.
[  255.376831] EFI: efi_query_variable_store, total size=131072., remain=19502.
[  255.414849] EFI: efi_query_variable_store, total size=131072., remain=19332.
[  255.500374] EFI: efi_query_variable_store, total size=131072., remain=18288.
[  255.538204] EFI: efi_query_variable_store, total size=131072., remain=18116.
[  255.623828] EFI: efi_query_variable_store, total size=131072., remain=17072.
[  255.662147] EFI: efi_query_variable_store, total size=131072., remain=16898.
[  255.829512] EFI: efi_query_variable_store, total size=131072., remain=15854.
[  255.868963] EFI: efi_query_variable_store, total size=131072., remain=15678.
[  256.036129] EFI: efi_query_variable_store, total size=131072., remain=14634.
[  256.062325] EFI: efi_query_variable_store, total size=131072., remain=14456.
[  256.229330] EFI: efi_query_variable_store, total size=131072., remain=13412.
[  256.270257] EFI: efi_query_variable_store, total size=131072., remain=13232.
[  256.437379] EFI: efi_query_variable_store, total size=131072., remain=12188.
[  256.477963] EFI: efi_query_variable_store, total size=131072., remain=12006.
[  256.644949] EFI: efi_query_variable_store, total size=131072., remain=10962.
[  256.672662] EFI: efi_query_variable_store, total size=131072., remain=10778.
[  256.840152] EFI: efi_query_variable_store, total size=131072., remain=9734.
[  256.881992] EFI: efi_query_variable_store, total size=131072., remain=9548.
[  256.967256] EFI: efi_query_variable_store, total size=131072., remain=8504.
[  257.008474] EFI: efi_query_variable_store, total size=131072., remain=8316.
[  257.093713] EFI: efi_query_variable_store, total size=131072., remain=7272.
[  257.138413] EFI: efi_query_variable_store, total size=131072., remain=7082.
[  257.305960] EFI: efi_query_variable_store, total size=131072., remain=6038.
[  257.348840] EFI: efi_query_variable_store, total size=131072., remain=5846.
[  275.674513] EFI: efi_query_variable_store, total size=131072., remain=17086.
[  275.717700] EFI: efi_query_variable_store, total size=131072., remain=16892.
[  275.803479] EFI: efi_query_variable_store, total size=131072., remain=15848.
[  275.846323] EFI: efi_query_variable_store, total size=131072., remain=15652.
[  275.931921] EFI: efi_query_variable_store, total size=131072., remain=14608.

When remain size greater than ~5kb it monotonously decrease. 
-- 
Best,
Madper Xie.