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SMMSTORE version 2 is a complete redesign of the current driver. It is
not backwards-compatible with version 1, and only one version can be
used at a time.
Key features:
* Uses a fixed communication buffer instead of writing to arbitrary
memory addresses provided by untrusted ring0 code.
* Gives the caller full control over the used data format.
* Splits the store into smaller chunks to allow fault tolerant updates.
* Doesn't provide feedback about the actual read/written bytes, just
returns error or success in registers.
* Returns an error if the requested operation would overflow the
communication buffer.
Separate the SMMSTORE into 64 KiB blocks that can individually be
read/written/erased. To be used by payloads that implement a
FaultTolerant Variable store like TianoCore.
The implementation has been tested against EDK2 master.
An example EDK2 implementation can be found here:
https://github.com/9elements/edk2-1/commit/eb1127744a3a5d5c8ac4e8eb76f07e79c736dbe2
Change-Id: I25e49d184135710f3e6dd1ad3bed95de950fe057
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Christian Walter <christian.walter@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40520
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
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