arch-arm: Update ARMv8.1-PAN to allow unprivileged instructions.

Update the ARMv8.1-PAN implementation to allow specified unprivileged
instructions to execute even when the cpsr.pan bit is set. The
specified instructions generate memory requests with the
TLB::ArmFlags::UserMode flags bit set.

See sections D5.4.2 (About PSTATE.PAN) and G5.6.2 (About the PAN bit)
of the Arm Architecture Reference Manual for details.
https://developer.arm.com/documentation/ddi0487/latest/

Change-Id: I9e904e0154de72c2e4cc70cbc49b3c8407a3cb1d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47779
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
2 files changed