Hi Waqar Ali,

It is possible for a secure service to be preempted by a NS interrupt. There are two main build options you may want to have a look at: https://git.trustedfirmware.org/plugins/gitiles/TF-M/trusted-firmware-m.git/... https://git.trustedfirmware.org/plugins/gitiles/TF-M/trusted-firmware-m.git/... These two should give you enough control on how to manage the scenario you described, the latter in particular.

Generally, interrupt priorities in TF-M are configured in the platform's specific tfm_interrupts.c, while the MPU/SAU/IDAU is usually set in target_cfg.c via tfm_hal_isolation_v8m.c (or equivalent). https://git.trustedfirmware.org/plugins/gitiles/TF-M/trusted-firmware-m.git/...

Hope that helps as a starting point.

Best regards Nicola

________________________________ From: Waqar Ali Tahir via TF-M tf-m@lists.trustedfirmware.org Sent: 01 August 2025 16:08 To: tf-m@lists.trustedfirmware.org tf-m@lists.trustedfirmware.org Cc: Ruchika Gupta ruchika.gupta_1@nxp.com Subject: [TF-M] Clarification on IRQ Preemption of Secure User Context by Non-Secure Interrupts

Dear TF-M Community,

I have a question regarding a specific use case involving interrupt handling and domain preemption in a TrustZone-enabled system using TF-M.

In the scenario where the processor is executing within a Secure user context (e.g., during Secure Partition execution), is it possible for an interrupt assigned to the Non-Secure domain to pre-empt this Secure execution?

* Does TF-M support such preemption by default? * If not supported out-of-the-box, what modifications or configuration changes would be required within TF-M to enable this behavior?

Any guidance on how TF-M manages interrupt priority and security attribution in this context would be greatly appreciated.

Best regards,

Waqar Ali

Waqar Ali Tahir

(He / Him / His)

Embedded SW Engineer

Phone: +433124 299160

Email: waqar.tahir@nxp.commailto:waqar.tahir@nxp.com

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