Even with today's ludicrously bloated kernels, I'm skeptical about the idea that speculative execution _in the kernel_ seriously helps computer performance. Has anyone measured overall slowdown from recompiling kernel branches to use LFENCE with new (fully serializing) microcode?
This is a red herring. These bugs affect both the kernel and userspace. Blanket protecting the kernel isn't going to fix the underlying problem once and for all.
