> It does take effort for an OS kernel to save and restore x87 state, so I could imagine somebody dropping support.
FXSAVE saves the x87 state with the SSE state, and XSAVE generalizes that to add several optional components, depending on what your processor support (as of right now, AVX state, MPX state, 3 for AVX-512, PT state, and SGX state, IIRC).
FXSAVE saves the x87 state with the SSE state, and XSAVE generalizes that to add several optional components, depending on what your processor support (as of right now, AVX state, MPX state, 3 for AVX-512, PT state, and SGX state, IIRC).