tree e411a969ab2cfcabc579b434419a30cf5ada66c0
parent 312e17ef99a0c999746b3e9b8f8a73d23ce54df3
author Dimitris Papastamos <dimitris.papastamos@arm.com> 1528367355 +0100
committer Dimitris Papastamos <dimitris.papastamos@arm.com> 1528454791 +0100

SDEI: Ensure SDEI handler executes with CVE-2018-3639 mitigation enabled

When dynamic mitigation is used, the SDEI handler is required to
execute with the mitigation enabled by default, regardless of the
mitigation state for lower ELs.  This means that if the kernel or
hypervisor explicitly disables the mitigation and then later when the
event is dispatched, the dispatcher will remember the mitigation state
for the lower ELs but force the mitigation to be on during the SDEI
handler execution.  When the SDEI handler returns, it will restore the
mitigation state.

This behaviour is described in "Firmware interfaces for mitigating
cache speculation vulnerabilities System Software on Arm Systems"[0].

[0] https://developer.arm.com/cache-speculation-vulnerability-firmware-specification

Change-Id: I8dd60b736be0aa9e832b0f92d67a401fdeb417f4
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>