powerpc: Add the ability to save FPU without giving it up
authorCyril Bur <cyrilbur@gmail.com>
Mon, 29 Feb 2016 06:53:49 +0000 (17:53 +1100)
committerMichael Ellerman <mpe@ellerman.id.au>
Wed, 2 Mar 2016 12:34:49 +0000 (23:34 +1100)
commit8792468da5e12e77e76e1edf081acf0392abb331
treee9fa424443bdba64726ccade9e5e169dd10c76ba
parentde2a20aa7237b45d3c14a2505804a8daa95a8f53
powerpc: Add the ability to save FPU without giving it up

This patch adds the ability to be able to save the FPU registers to the
thread struct without giving up (disabling the facility) next time the
process returns to userspace.

This patch optimises the thread copy path (as a result of a fork() or
clone()) so that the parent thread can return to userspace with hot
registers avoiding a possibly pointless reload of FPU register state.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
arch/powerpc/include/asm/switch_to.h
arch/powerpc/kernel/fpu.S
arch/powerpc/kernel/process.c