All it takes for data to end up in L1 cache is to access it (even only once) You don't have to access it in a special way to make it end up in L1. What you have to do for cache side channel attacks is to force data out of the cache, you can tell when the some other data gets in. This can get quite noisy if there is a lot of contention to the same cache lines. Also remember that the information leak is not in the contents of the cached data, but in the address being cached.