Core: Enable SPE preemption by NSPE
Enable Non-secure interrupts to preempt Secure thread mode.
This is done by not disabling Non-secure interrupts when entering
Secure service.
Change-Id: I99ab50b153e60ed68f67aa4d1f1cb033a6c8c022
Signed-off-by: Mate Toth-Pal <mate.toth-pal@arm.com>
diff --git a/docs/user_guides/tfm_integration_guide.rst b/docs/user_guides/tfm_integration_guide.rst
index 5d0e80d..df8a87a 100644
--- a/docs/user_guides/tfm_integration_guide.rst
+++ b/docs/user_guides/tfm_integration_guide.rst
@@ -125,6 +125,17 @@
See
:doc:`ns client identification documentation <tfm_ns_client_identification>`.
+*********************
+Non-secure interrupts
+*********************
+Non-secure interrupts are allowed to preempt Secure thread mode.
+With the current implementation, a NSPE task can spoof the identity of another
+NSPE task. This is an issue only when NSPE has provisions for task isolation.
+Note, that ``AIRCR.PRIS`` is still set to restrict the priority range available
+to NS interrupts to the lower half of available priorities so that it wouldn't
+be possible for any non-secure interrupt to preempt a higher-priority secure
+interrupt.
+
--------------
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