tree 3bd4dc212475d127858631ac355d245f749acc51
parent 696ed4fdf5c7db00450075c5407de7ff1ef1e854
author Manish Pandey <manish.pandey2@arm.com> 1685018774 +0100
committer Manish Pandey <manish.pandey2@arm.com> 1698837081 +0000

feat(el3-runtime): modify vector entry paths

Vector entries in EL3 from lower ELs, first check for any pending
async EAs from lower EL before handling the original exception.
This happens when there is an error (EA) in the system which is not
yet signaled to PE while executing at lower EL. During entry into EL3
the errors (EA) are synchronized causing async EA to pend at EL3.

On detecting the pending EA (via ISR_EL1.A) EL3 either reflects it back
to lower EL (KFH) or handles it in EL3 (FFH) based on EA routing model.

In case of Firmware First handling mode (FFH), EL3 handles the pended
EA first before returing back to handle the original exception.

While in case of Kernel First handling mode (KFH), EL3 will return back
to lower EL without handling the original exception. On returing to
lower EL, EA will be pended. In KFH mode there is a risk of back and
forth between EL3 and lower EL if the EA is masked at lower EL or
priority of EA is lower than that of original exception. This is a
limitation in current architecture but can be solved in future if EL3
gets a capability to inject virtual SError.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I3a2a31de7cf454d9d690b1ef769432a5b24f6c11