Re: grub causing NVDIMMs to be treated as normal memory

[Seth Goldberg]

 It may operate the same, but there may be persistent data in there that the OS 
wants to preserve across reboots.

 —S

On Nov 25, 2015, at 6:08 AM, Andrei Borzenkov <address@hidden> wrote:

> On Wed, Nov 25, 2015 at 2:52 AM, Elliott, Robert (Persistent Memory)
> <address@hidden> wrote:
>> We've noticed that some combinations of grub and old linux kernels
>> 
>> end up interpreting the UEFI memory map EfiPersistentMemory type 14
>> 
>> (formerly a reserved value) as regular memory in the linux e820
>> 
>> table, causing silent data corruption on the NVDIMMs.  That occurs
>> 
>> even though grub prints this message suggesting everything is safe:
>> 
>>    Unknown memory type 14, considering reserved
>> 
>> 
>> 
>> In broken versions of grub, the code parsing the UEFI memory map
>> 
>> has a "default" case that falls through to the
>> 
>> GRUB_EFI_BOOT_SERVICES_DATA case,
> 
> This is fallout of 9be4c45dbe3c877d1f4856e99ee15133c6cd2261; thank you
> for report!
> 
>> which marks the memory range
>> 
>> as GRUB_MEMORY_AVAILABLE and ends up in e820 as regular memory.
>> 
> 
> According to EFI spec, EfiPersistentMemory is "A memory region that
> operates as EfiConventionalMemory". Why it should be treated
> differently?
> 
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