With that said, all in-kernel SSE is done with interrupts disabled. The registers are saved and restored by the critical section. This is by no means exclusive to Linux. Other kernels do it too. Illumos and FreeBSD come to mind here. The Linux kernel functions for doing this are kernel_fpu_begin()/kernel_fpu_end().
No announcement yet.
Torvalds Is Unconvinced By LTO'ing A Linux Kernel