[PATCH v8 4/4] efi_vars: Implement SPI Flash store

[Ilias Apalodimas]

[...]

> >>> +
> >>>   config EFI_MM_COMM_TEE
> >>>       bool "UEFI variables storage service via the trusted world"
> >>>       depends on OPTEE
> >>> @@ -153,7 +171,7 @@ endchoice
> >>>   config EFI_RT_VOLATILE_STORE
> >>>       bool "Allow variable runtime services in volatile storage (e.g RAM)"
> >>> -    depends on EFI_VARIABLE_FILE_STORE
> >>> +    depends on EFI_VARIABLE_FILE_STORE || EFI_VARIABLE_SF_STORE
> >>
> >> Hello Michal,
> >>
> >> If the backend store is SPI flash, we should not publish the variable "RTStorageVolatile" at runtime as currently defined.
> >>
> >> For the background see this commit for the efivar library:
> >>
> >> https://github.com/rhboot/efivar/commit/68daa04654acbe1bbaa17ebfc23c371b39e69c6b
> >>
> >> The first three patches look correct to me and I will add them to a merge request for efi-next.
> >
> >Do I read it that when I don't allow to select EFI_RT_VOLATILE_STORE you will be fine with the patch itself?
>
> This was my only concern.
>
> Maybe setting the file name to /dev/mtd/by-name/<partition name> would work with efivar. But I have not tested it.

I don't think it wiill. That variables describes the filename relative
to the ESP

>
> In U-Boot we could replace EFI_VARIABLE_SF_DEVICE_INDEX, SIZE, and OFFSET by a partition name, too. That way it would be the common device-tree for U-Boot and Linux controlling the placement of the variables store.
>
> >
> >
> >> The usage of efi_var_mem_ins() and efi_var_mem_del() when SetVariable() does not change anything is not flash-friendly. Michal, do you want to have a look at this area?
> >
> >That's known limitation describe in EFI_VARIABLE_SF_STORE Kconfig Note.
>
> This could be a topic for future work.
>
> Best regards

Cheers
/Ilias
>
> Heinrich
>