Some designs which wish to make use of a secure execution environment may be based on multi-processor ARM designs, such as the Cortex-A9 MPCore processor. These systems allow higher software performance by concurrently executing threads on multiple hardware processors, which makes them ideal for processing intensive tasks such as software media CODEC processing.
The Secure world software architect has an important decision to make here - how will the Secure world software make use of multiple processors?
Most security systems aim to use a simple software design because simplicity means that there is less risk of a software bug which exposes a security vulnerability. Genuine multi-threading adds a layer of software complexity which is often hard to test because of the timing-sensitivity it introduces. For this reason many Secure world software implementations may choose to implement a single-processor Secure world which makes little or no use of the SMP processor features, even if the Normal world is running using full SMP mode.