[coreboot-gerrit] Change in ...coreboot[master]: riscv: fix run_payload

[Philipp Hug (Code Review)]

Philipp Hug has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/33462 )

Change subject: riscv: fix run_payload
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Patch Set 2:
> Patch Set 2:
> > Patch Set 2: Code-Review+1
> >
> > Thanks!
> > Please change "riscv: fix run_payload" to something more specific.
>
> Do you have suggest?
> > Also mention how the change has been tested.
>
> I read this code and found a logic error when setting the MPP field of mstatus.
> If you do not return via mret, MPIE will not work.
> I have only tested the situation of return to M-Mode.

e.g.

riscv: use mret to invoke M-mode payload and disable interrupts

Fixes a logic error that sets MPIE, but didn't use mret to return to the payload. This left MIE set to an undefined value.

Now all modes are handled the same way:
* Trap vector base address point to the payload
* Disable Interrupt
* Return to payload using mret

TEST=Run an M-mode payload