Hi Mark,
On Thu, Dec 14, 2023 at 05:47:42PM +0100, Mark Kettenis wrote:
Date: Thu, 14 Dec 2023 15:53:46 +0000 From: Abdellatif El Khlifi abdellatif.elkhlifi@arm.com
Hi Abdellatif,
Hi guys,
I'd like to ask for advice regarding adding EFI RT support to the Arm's FF-A bus in U-Boot.
The objective is to enable the FF-A messaging APIs in EFI RT to be used for comms with the secure world. This will help getting/setting EFI variables through FF-A.
The existing FF-A APIs in U-Boot call the DM APIs (which are not available at RT).
Two possible solutions:
1/ having the entire U-Boot in RT space (as Simon stated in this discussion[1])
I don't think this is a terribly good idea. With this approach orders of magnitude more code will be present in kernel address space one the OS kernel is running and calling into the EFI runtime. Including code that may access hardware devices that are now under OS control. It will be nigh impossible to audit all that code and make sure that only a safe subset of it gets called. So...
2/ Create an RT variant for the FF-A APIs needed. These RT variant don't call the DM APIs (e.g: ffa_mm_communicate_runtime, ffa_sync_send_receive_runtime, ...)
What do you recommend please ?
...this is what I would recommend. Preferably in a way that refactors the code such that the low-level functionality is shared between the DM and non-DM APIs.
That's my preferred solution, thanks.
Cheers, Abdellatif