x86/fpu: Fix FNSAVE usage in eagerfpu mode
authorAndy Lutomirski <luto@kernel.org>
Sun, 24 Jan 2016 22:38:07 +0000 (14:38 -0800)
committerIngo Molnar <mingo@kernel.org>
Tue, 9 Feb 2016 14:42:55 +0000 (15:42 +0100)
commit5ed73f40735c68d8a656b46d09b1885d3b8740ae
treee0de0bf276aee1b44370b90dc6f3e0895ab5b6d1
parent4ecd16ec7059390b430af34bd8bc3ca2b5dcef9a
x86/fpu: Fix FNSAVE usage in eagerfpu mode

In eager fpu mode, having deactivated FPU without immediately
reloading some other context is illegal.  Therefore, to recover from
FNSAVE, we can't just deactivate the state -- we need to reload it
if we're not actively context switching.

We had this wrong in fpu__save() and fpu__copy().  Fix both.
__kernel_fpu_begin() was fine -- add a comment.

This fixes a warning triggerable with nofxsr eagerfpu=on.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: yu-cheng yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/60662444e13c76f06e23c15c5dcdba31b4ac3d67.1453675014.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/x86/kernel/fpu/core.c