Re: [Xenomai] I-pipe's determinism in handling hardware interrupts when GIC implements "Security Extensions"

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2015-08-14 22:38, Hongfei Cheng wrote:
>> If, like I believe,
>> such a "privileged interrupt" is handled by the monitor behind
>> Linux/I-pipe's back, then yes, it will break determinism.
> 
> Do you have any suggestion as to how I-pipe can be improved to work
> with ARM's multiple exception levels in order to ensure determinism on
> ARMv7 (and ARMv8)?

Conceptually, this is fairly similar to the SMM on x86. But, in contrast
to that arch, we tend to have the firmware sources on ARM.

You can check if you actually need the secure monitor on our platform
(it's most often used for PSCI) and disable it (may be trickier on ARMv8
where PSCI is mandatory IIRC) or patch it or the kernel to avoid the
problematic service calls (specifically CPU power control via PSCI).

Jan

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