Hi Michel,

The simultaneous NS call has not been supported yet. Currently TF-M based on trustzone will panic when re-entry from NS is detected. So only one context for secure service call from NS task is allowed. In the NS reference implementation, tfm_ns_interface_dispatchhttps://git.trustedfirmware.org/TF-M/tf-m-tests.git/tree/app/tfm_ns_interface.c#n18 ensures that only one thread calls secure service.

BR, Xinyu

From: Michel JAOUEN via TF-M tf-m@lists.trustedfirmware.org Sent: Monday, November 28, 2022 6:43 PM To: David Wang David.Wang@arm.com; 'tf-m@lists.trustedfirmware.org' tf-m@lists.trustedfirmware.org Subject: [TF-M] Number context for NS

Hello, I see that in coming 1.7.0 the file secure_fw/spm/ns_client_ext/tfm_ns_ctx.h contains a comment /* Supported maximum context for NS. Only support single context for now. */ #define TFM_NS_CONTEXT_MAX 1 Does it mean that several simultaneous NSC call is not supported ? Best regards

ST Restricted