Building on the Metldown approach, Foreshadow exploits abandoned cache state changes associated with accessing contents of the Intel SGX secure enclave. They show that user space code can violate aspects of SGX and, since SGX is designed to protect against compromised root level code, they show that with root level privileges, it is possible to further optimize the exploit and to read out the content of an enclave, without even executing it. 

Another exploit takes advantage of simply observing the timing behavior of a key cache line in a shared page by frequently evicting it and seeing whether the victim loads it as a result of a data dependent branch. The SHARP variant of cache coherence protocols addresses this by prioritizing eviction of non-shared lines, then one-way shared, then defaulting to random replacement. It uses existing status for directory based coherence to deterine sharing status. 

I will be away at a conference next Tuesday, so there will be no class. We will start looking at parallelism on Thursday. 

Slides are here