linux-kernel - [PATCH 168/208] x86/fpu: Simplify fpstate_sanitize

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Date:	Tue,  5 May 2015 19:57:52 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	linux-kernel@...r.kernel.org
Cc:	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 168/208] x86/fpu: Simplify fpstate_sanitize_xstate() calls

Remove the extra layer of __fpstate_sanitize_xstate():

	if (!use_xsaveopt())
		return;
	__fpstate_sanitize_xstate(tsk);

and move the check for use_xsaveopt() into fpstate_sanitize_xstate().

In general we optimize for the presence of CPU features, not for
the absence of them. Furthermore there's little point in this inlining,
as the call sites are not super hot code paths.

Doing this uninlining shrinks the code a bit:

   text    data     bss     dec     hex filename
   14108751        2573624 1634304 18316679        1177d87 vmlinux.before
   14108627        2573624 1634304 18316555        1177d0b vmlinux.after

Also remove a pointless '!fx' check from fpstate_sanitize_xstate().

Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/fpu/internal.h | 9 +--------
 arch/x86/kernel/fpu/xstate.c        | 4 ++--
 2 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 6b6fa46037f8..88fec3f108de 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -139,14 +139,7 @@ static inline void fx_finit(struct i387_fxsave_struct *fx)
 	fx->mxcsr = MXCSR_DEFAULT;
 }
 
-extern void __fpstate_sanitize_xstate(struct task_struct *);
-
-static inline void fpstate_sanitize_xstate(struct task_struct *tsk)
-{
-	if (!use_xsaveopt())
-		return;
-	__fpstate_sanitize_xstate(tsk);
-}
+extern void fpstate_sanitize_xstate(struct task_struct *);
 
 #define user_insn(insn, output, input...)				\
 ({									\
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index fc2ff1239fea..47b9591947e1 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -92,13 +92,13 @@ EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
  * if the corresponding header bit is zero. This is to ensure that user-space doesn't
  * see some stale state in the memory layout during signal handling, debugging etc.
  */
-void __fpstate_sanitize_xstate(struct task_struct *tsk)
+void fpstate_sanitize_xstate(struct task_struct *tsk)
 {
 	struct i387_fxsave_struct *fx = &tsk->thread.fpu.state.fxsave;
 	int feature_bit;
 	u64 xfeatures;
 
-	if (!fx)
+	if (!use_xsaveopt())
 		return;
 
 	xfeatures = tsk->thread.fpu.state.xsave.header.xfeatures;
-- 
2.1.0

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