[tip:x86/fpu] x86/fpu: Use restore_init_xstate() instead of math_state_restore() on kthread exec

[tip-bot for Oleg Nesterov]

Commit-ID:  9cb6ce823bbd1adbe15e30bd1435c84c2e271767
Gitweb:     http://git.kernel.org/tip/9cb6ce823bbd1adbe15e30bd1435c84c2e271767
Author:     Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Wed, 11 Mar 2015 18:34:49 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 23 Mar 2015 10:13:58 +0100

x86/fpu: Use restore_init_xstate() instead of math_state_restore() on kthread exec

Change flush_thread() to do user_fpu_begin() and restore_init_xstate()
instead of math_state_restore().

Note: "TODO: cleanup this horror" is still valid. We do not need
init_fpu() at all, we only need fpu_alloc() and memset(0). But this
needs other changes, in particular user_fpu_begin() should set
used_math().

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Pekka Riikonen <priikone@xxxxxx>
Cc: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Suresh Siddha <sbsiddha@xxxxxxxxx>
Link: http://lkml.kernel.org/r/20150311173449.GE5032@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/process.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index dcaf4b0..6b05829 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -143,7 +143,8 @@ void flush_thread(void)
 		/* kthread execs. TODO: cleanup this horror. */
 		if (WARN_ON(init_fpu(current)))
 			force_sig(SIGKILL, current);
-		math_state_restore();
+		user_fpu_begin();
+		restore_init_xstate();
 	}
 }
 
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