HI Tom,
On Fri, Jul 28, 2023 at 09:54:15AM -0400, Tom Rini wrote:
On Fri, Jul 28, 2023 at 02:00:25PM +0300, Ilias Apalodimas wrote:
Hi Tom
On Thu, 27 Jul 2023 at 19:43, Tom Rini trini@konsulko.com wrote:
On Thu, Jul 27, 2023 at 05:07:11PM +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
Changelog:
v17:
- show a debug message rather than an error when FF-A is not detected
[snip]
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig index c5835e6ef6..8fbadb9201 100644 --- a/lib/efi_loader/Kconfig +++ b/lib/efi_loader/Kconfig @@ -55,13 +55,53 @@ config EFI_VARIABLE_FILE_STORE stored as file /ubootefi.var on the EFI system partition.
config EFI_MM_COMM_TEE
bool "UEFI variables storage service via OP-TEE"depends on OPTEE
bool "UEFI variables storage service via the trusted world"depends on OPTEE && ARM_FFA_TRANSPORTYou didn't get my changes in here however. If you can do EFI_MM_COMM_TEE without ARM_FFA_TRANSPORT (as lx2160ardb_tfa_stmm_defconfig does) then you don't make this option depend on . If FF-A is only for use here, you make FF-A depend on this, and the FF-A specific variable depend on ARM_FFA_TRANSPORT.
Abdellatif hinted at what's going on here. When I added this Kconfig option to lx2160 FF-A wasn't implemented yet.
The defconfig has existed since May 2020, which is when you added EFI_MM_COMM_TEE itself too. So I think it's that no one did the check I did until now and saw this series was disabling what was on the other platform.
Since FF-A isn't a new communication mechanism but builds upon the existing SMCs to build an easier API, I asked Abdellatif to hide this complexity. We had two options, either make Kconfig options for either FF-A or the traditional SMCs and remove the dependencies, or piggyback on FF-As discovery mechanism and make the choice at runtime. The latter has a small impact on code size, but imho makes developers' life a lot easier.
I'm not sure how much you can do a run-time option here since you're setting a bunch of default values for FF-A to 0 in Kconfig. If we're supposed to be able to get them at run time, we shouldn't need a Kconfig option at all. I'm also not sure how valid a use case it is where we won't know at build time what the rest of the firmware stack supports here.
That's a fair point. FF-A in theory has APIs to discover memory. Abdellatif, why do we need the Kconfigs for shared memory on FF-A?
Regards /Ilias
-- Tom