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SubjectRe: [BUG]: DELL XPS 8500 become a brick after fill too many entries to nvram.
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matt@console-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.[unhandled content-type:application/octet-stream]
> - 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.
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