Re: grub causing NVDIMMs to be treated as normal memory

[Andrei Borzenkov <arvidjaar@gmail.com>]

On Fri, Nov 27, 2015 at 2:08 PM, Vladimir 'φ-coder/phcoder' Serbinenko
<phcoder@gmail.com> wrote:
> What about this patch for the passing of pram?

It is incomplete. You need to handle make_efi_memtype() as well as
efiemu where I am not sure what is the right thing to do (and we
probably have zero chance to test it in real life anyway).

> diff --git a/grub-core/mmap/efi/mmap.c b/grub-core/mmap/efi/mmap.c
> index 900a4d6..0c03c5d 100644
> --- a/grub-core/mmap/efi/mmap.c
> +++ b/grub-core/mmap/efi/mmap.c
> @@ -118,6 +118,12 @@ grub_efi_mmap_iterate (grub_memory_hook_t hook,
> void *hook_data,
>                 GRUB_MEMORY_NVS, hook_data);
>           break;
>
> +       case GRUB_EFI_PERSISTENT_MEMORY:
> +         hook (desc->physical_start, desc->num_pages * 4096,
> +               GRUB_MEMORY_PRAM, hook_data);
> +         break;
> +
> +

Extra empty line.

>         default:
>           grub_printf ("Unknown memory type %d, considering reserved\n",
>                        desc->type);
> diff --git a/include/grub/efi/api.h b/include/grub/efi/api.h
> index 24a05c5..2bbfe34 100644
> --- a/include/grub/efi/api.h
> +++ b/include/grub/efi/api.h
> @@ -476,6 +476,7 @@ enum grub_efi_memory_type
>      GRUB_EFI_MEMORY_MAPPED_IO,
>      GRUB_EFI_MEMORY_MAPPED_IO_PORT_SPACE,
>      GRUB_EFI_PAL_CODE,
> +    GRUB_EFI_PERSISTENT_MEMORY,
>      GRUB_EFI_MAX_MEMORY_TYPE
>    };
>  typedef enum grub_efi_memory_type grub_efi_memory_type_t;
> diff --git a/include/grub/memory.h b/include/grub/memory.h
> index 083cfb6..1003a9c 100644
> --- a/include/grub/memory.h
> +++ b/include/grub/memory.h
> @@ -30,6 +30,7 @@ typedef enum grub_memory_type
>      GRUB_MEMORY_ACPI = 3,
>      GRUB_MEMORY_NVS = 4,
>      GRUB_MEMORY_BADRAM = 5,
> +    GRUB_MEMORY_PRAM = 7,

GRUB_MEMORY_PERSISTENT is probably more clear.

>      GRUB_MEMORY_COREBOOT_TABLES = 16,
>      GRUB_MEMORY_CODE = 20,
>      /* This one is special: it's used internally but is never reported
>>>> Note (b): The internal GRUB_MEMORY_CODE (20) value is
>>>> leaking through to the E820 table.
>>>>
>>>> That appears to be from this patch on 2013-10-14:
>>>>     6de9ee86 Pass-through unknown E820 types
>>>
>>> If we are discussing ACPI 6.0 systems here, it explicitly says that
>>> values above 12 should be treated as reserved. Does it cause
>>> problems?
>>
>> All undefined values are reserved for future standardization;
>> the meaning they might have in the future is unpredictable.
>>
>> Software compatible with ACPI 6.0 is supposed to treat them as
>> reserved, but software compatible with a future version of ACPI
>> might interpret them as having some different meaning that isn't
>> compatible with GRUB_MEMORY_CODE.
>>
>> Some companies used e820 type 12 to mean persistent memory without
>> getting that assigned by the ACPI WG, so that value was
>> contaminated.  We should probably mark 20 as contaminated too,
>> given this issue.
>>
> I see now that we have leaked 16 (coreboot tables) as well. Could we
> mark 16 as contaminated as well?
> For memory code: should we just pass reserved in linux e820 or is it
> better to keep doing this bug given possible reliance on it by other
> software?

I think it is better to leave it as is as long as those values can be reserved.