The explanation is at end of page 4 and begin of page 5 on the meltdown paper. In a nutshell, the speculative feature allows the read to happen, it "doesn't seg

The explanation is at end of page 4 and begin of page 5 on the meltdown paper. In a nutshell, the speculative feature allows the read to happen, it "doesn't segfault," and only signals the OS of the segfault or whatever until it's actually executed.