Clarification on Thread Behavior in Intel SGX Enclave

I have been reading the Intel SGX Developer Guide _(https://download.01.org/intel-sgx/latest/linux-latest/docs/Intel_SGX_Developer_Guide.pdf, Thu 12 Sep 2024 05:51:39 AM UTC)_ and encountered some confusion regarding thread behavior in the enclave.

Here are the specific sections causing my confusion:

1. P30-P31: In Table 8, "Summary of Intel® SGX Rules and Limitations," it mentions:
_"Threading support is Partially. **Creating threads inside the enclave is not supported**. Threads that run inside the enclave are created within the (untrusted) application. Spin-locks, trusted mutex, and condition variables API can be used for thread synchronization inside the enclave."_

2. P144: In the section about **pthreads**, it states:
_"The Intel® Software Guard Extensions (Intel® SGX) SDK includes a **trusted version** of the pthreads library. The library is named sgx_pthread and can **only be used inside an enclave**."_

Questions:

- Does this mean threads cannot be created or used directly inside the enclave?
- How does the sgx_pthread library work in this context, and in what specific scenarios can it be used inside the enclave?
- For applications that depend heavily on multi-threading for performance optimization, what are the recommended strategies when using an SGX enclave? Alternatively, should I consider a different platform, such as Confidential-VM technologies like TDX?

Any clarification or guidance on how to approach multi-threading in an SGX environment would be greatly appreciated. Thank you for your assistance!

Start with the Intel SGX Developer Guide sections cited in the issue: pages 30–31 on threading limitations and page 144 on the trusted sgx_pthread library. Compare those statements and investigate the requested threading scenarios and SGX-versus-TDX considerations; done means providing a clear, documented explanation and guidance.

Written by the indexing model from the issue text.