To be more clear, I wouldn't call this "UEFI in EL3" since UEFI is really the OS/driver interface, instead I would call it something like "SEC/PEI in EL3". Note that SEC and PEI are described in the PI specification and don't existing in the UEFI specification.

We too are looking at this same issue, specifically trying to see if we can the SEC and PEI phases at EL3 and bootstrap Trusted Firmware a bit later in boot, allowing us to keep the PI-spec ways of doing things (PEI memory init, HOBs, PPIs, edk2 build system, etc).

In this case it doesn't seem appropriate for the edk2 ARM support libraries to force the ARM Trusted Firmware design onto implementations since it is their choice whether to go the TF direction or some other direction so I would recommend the code is updated to remove this restriction.

Eugene

-----Original Message----- From: boot-architecture-bounces@lists.linaro.org [mailto:boot-architecture-bounces@lists.linaro.org] On Behalf Of bhupesh.sharma@freescale.com Sent: Monday, August 04, 2014 4:25 AM To: edk2-devel@lists.sourceforge.net; olivier.martin@arm.com Cc: boot-architecture@lists.linaro.org; Sakar.Arora@freescale.com Subject: AARCH64 UEFI and EL3

Hi,

The current AARCH64 UEFI is designed to run entirely in EL2 with the assumption that the ARM Trusted FW (ATF) running in EL3 and launching UEFI in EL2.

As a result if we try to use the UEFI bootloader as a bare-metal debug tool (w/o the ATF, BootROM and so on..), we get an assertion failure in ArmConfigureMmu call (PEI phase).

"UEFI should not run in EL3".

However when I look at 'ArmPkg/Library/ArmLib/Common/AArch64/ArmLibSupport.S', I see some function implementations support UEFI running in EL3...

ASM_PFX(ArmSetTTBR0): EL1_OR_EL2_OR_EL3(x1) 1:msr ttbr0_el1, x0 // Translation Table Base Reg 0 (TTBR0) b 4f 2:msr ttbr0_el2, x0 // Translation Table Base Reg 0 (TTBR0) b 4f 3:msr ttbr0_el3, x0 // Translation Table Base Reg 0 (TTBR0) 4:isb ret

...But others in the same file, don't seem to support UEFI running in EL3:

ASM_PFX(ArmGetTTBR0BaseAddress): EL1_OR_EL2(x1) 1:mrs x0, ttbr0_el1 b 3f 2:mrs x0, ttbr0_el2 3:LoadConstantToReg(0xFFFFFFFFFFFF, x1) /* Look at bottom 48 bits */ and x0, x0, x1 isb ret

Does UEFI provide some placeholders to make vendor specific changes in the SEC or PEI phase to enable execution in EL3 mode?

Last I gathered from the discussions on the UEFI mailing lists, it seems that the some changes in PEI specs is required to accommodate ARM Trusted Firmware (ATF) and UEFI running in EL2. Where can I get more information on the same

Regards, Bhupesh

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