Hi Tom,
On Wed, Jul 26, 2023 at 03:39:12PM -0400, Tom Rini wrote:
On Wed, Jul 26, 2023 at 10:45:02AM +0100, Abdellatif El Khlifi wrote:
Add MM communication support using FF-A transport
This feature allows accessing MM partitions services through EFI MM communication protocol. MM partitions such as StandAlonneMM or smm-gateway secure partitions which reside in secure world.
An MM shared buffer and a door bell event are used to exchange the data.
The data is used by EFI services such as GetVariable()/SetVariable() and copied from the communication buffer to the MM shared buffer.
The secure partition is notified about availability of data in the MM shared buffer by an FF-A message (door bell).
On such event, MM SP can read the data and updates the MM shared buffer with the response data.
The response data is copied back to the communication buffer and consumed by the EFI subsystem.
MM communication protocol supports FF-A 64-bit direct messaging.
Signed-off-by: Abdellatif El Khlifi abdellatif.elkhlifi@arm.com Tested-by: Gowtham Suresh Kumar gowtham.sureshkumar@arm.com Reviewed-by: Simon Glass sjg@chromium.org Cc: Tom Rini trini@konsulko.com Cc: Ilias Apalodimas ilias.apalodimas@linaro.org Cc: Jens Wiklander jens.wiklander@linaro.org
So, at this point in the series we impact lx2160ardb_tfa_stmm which is the only config in the tree prior to this series that sets CONFIG_EFI_MM_COMM_TEE. I'm not going to block this series[1] on updating lx2160ardb_tfa_stmm as well, but I do want to make sure the maintainers there are aware and can update the config to support the current state of this technology.
[1]: https://patchwork.ozlabs.org/project/uboot/list/?series=365876&state=*
Following a decision made with Ilias, the new MM comms design works as follows:
- Try to communicate using FF-A bus first - If that fails, try to communicate using Optee. So, platforms that don't support FF-A in the Secure side can still use Optee communication
This is done through the code below [1].
This logic needs CONFIG_ARM_FFA_TRANSPORT=y in the defconfig.
I added CONFIG_ARM_FFA_TRANSPORT=y to lx2160ardb_tfa_stmm_defconfig, CONFIG_EFI_MM_COMM_TEE is enabled and it builds fine.
Is it expected that lx2160ardb_tfa_stmm maintainers add CONFIG_ARM_FFA_TRANSPORT=y to lx2160ardb_tfa_stmm_defconfig ?
Cheers Abdellatif
[1]: Selecting the MM comms method:
static efi_status_t mm_communicate(u8 *comm_buf, efi_uintn_t dsize) ... mm_comms = get_mm_comms(); if (mm_comms == MM_COMMS_FFA) ret = ffa_mm_communicate(comm_buf, dsize); else ret = optee_mm_communicate(comm_buf, dsize);