Mailing the story:
Linus Torvalds' Latest Commentary Against -O3'ing The Linux Kernel
This shouldn't be too surprising considering some of Linus Torvalds past commentary about compiler optimizations and bad experiences long ago with GCC, but Linus Torvalds is not interested in seeing a tunable Kconfig option for using the -O3 compiler optimization level for building the Linux kernel without substantial justification.