Intel® SGX does not provide explicit protection from side-channel attacks. It is the enclave developer's responsibility to address side-channel attack concerns.
In general, enclave operations that require an OCall, such as thread synchronization, I/O, etc., are exposed to the untrusted domain. If using an OCall would allow an attacker to gain insight into enclave secrets, then there would be a security concern. This scenario would be classified as a side-channel attack, and it would be up to the ISV to design the enclave in a way that prevents the leaking of side-channel information.
An attacker with access to the platform can see what pages are being executed or accessed. This side-channel vulnerability can be mitigated by aligning specific code and data blocks to exist entirely within a single page.
More important, the application enclave should use an appropriate crypto implementation that is side channel attack resistant inside the enclave if side-channel attacks are a concern.
The Intel® Advanced Encryption Standard New Instructions (Intel® AES-NI) Set is designed to be constant time to prevent timing based side channel attacks.