What I don't understand is: Why is this close coexistence with a untrusted code necessary or even beneficial?
People run code from different security domains on the same L1/L2 cache. Why is that beneficial? Compared to, say, having the kernel flush the cache entirely whenever a context switch goes from one (uid/chroot/...) tuple to another, and only running processes/threads with the same tuple on the same cache at the same time?
People run code from different security domains on the same L1/L2 cache. Why is that beneficial? Compared to, say, having the kernel flush the cache entirely whenever a context switch goes from one (uid/chroot/...) tuple to another, and only running processes/threads with the same tuple on the same cache at the same time?