[U-Boot] [RFC 1/1] efi_loader: refactor switch to hypervisor mode

[Heinrich Schuchardt]

On 12/25/18 1:39 PM, Mark Kettenis wrote:
>> From: Heinrich Schuchardt <xypron.glpk at gmx.de>
>> Date: Tue, 25 Dec 2018 09:26:57 +0100
>>
>> Refactor the switch from supervisor to hypervisor to a new function called at
>> the beginning of do_bootefi().
>>
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>> ---
>> With this patch I am just moving around the switch from supervisor to
>> hypervisor mode within the EFI subsystem. Similar switching also occurs
>> in all other boot commands (cf. arch/arm/lib/bootm.c).
> Never been a huge fan of setjmp/longjmp, but I can see what you're
> doing here.  This is tricky code though, so I think this needs to be
> tested on armv7 systems that support virtualisation (Cortex-A7) and
> systems that don't (Cortex-A9).

For

> 
>> Why are we running the U-Boot console in supervisor mode at all? Wouldn't
>> it be advisable for security reasons to switch to hypervisor mode before
>> entering the console?
> On some boards there are commands that access secure devices.  So
> those commands would no longer work.  Obviously that is already the
> case when an EFI payload returns to the U-Boot command prompt.
> 

Thanks Mark for pointing this out.

We have some major differences between bootm and bootefi:

- Bootefi does not support CONFIG_ARMV8_SWITCH_TO_EL1 used by some
  Xilinx boards.
- It ignores CONFIG_ARMV8_PSCI.
- Update_os_arch_secondary_cores() is not called (needed for preparing
  SMP on several NXP platforms). I think these are maintained by York.

So uniting the code might be advisable.

Best regards

Heinrich