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.elkhl...@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
