[tip:x86/fpu] x86/fpu: Decouple fpregs_activate()/fpregs_deactivate() from fpu->fpregs_active

[tip-bot for Ingo Molnar]

Commit-ID:  6cf4edbe0526db311a28734609da888fdfcb3604
Gitweb:     http://git.kernel.org/tip/6cf4edbe0526db311a28734609da888fdfcb3604
Author:     Ingo Molnar <mi...@kernel.org>
AuthorDate: Sat, 23 Sep 2017 15:00:02 +0200
Committer:  Ingo Molnar <mi...@kernel.org>
CommitDate: Sun, 24 Sep 2017 13:04:34 +0200

x86/fpu: Decouple fpregs_activate()/fpregs_deactivate() from fpu->fpregs_active

The fpregs_activate()/fpregs_deactivate() are currently called in such a 
pattern:

        if (!fpu->fpregs_active)
                fpregs_activate(fpu);

        ...

        if (fpu->fpregs_active)
                fpregs_deactivate(fpu);

But note that it's actually safe to call them without checking the flag first.

This further decouples the fpu->fpregs_active flag from actual FPU logic.

Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Dave Hansen <dave.han...@linux.intel.com>
Cc: Eric Biggers <ebigge...@gmail.com>
Cc: Fenghua Yu <fenghua...@intel.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Oleg Nesterov <o...@redhat.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Rik van Riel <r...@redhat.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng...@intel.com>
Link: http://lkml.kernel.org/r/20170923130016.21448-20-mi...@kernel.org
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
 arch/x86/include/asm/fpu/internal.h | 7 +------
 arch/x86/kernel/fpu/core.c          | 3 +--
 2 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h 
b/arch/x86/include/asm/fpu/internal.h
index 7fa676f..42a6016 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -526,8 +526,6 @@ static inline int fpregs_state_valid(struct fpu *fpu, 
unsigned int cpu)
  */
 static inline void fpregs_deactivate(struct fpu *fpu)
 {
-       WARN_ON_FPU(!fpu->fpregs_active);
-
        fpu->fpregs_active = 0;
        this_cpu_write(fpu_fpregs_owner_ctx, NULL);
        trace_x86_fpu_regs_deactivated(fpu);
@@ -535,8 +533,6 @@ static inline void fpregs_deactivate(struct fpu *fpu)
 
 static inline void fpregs_activate(struct fpu *fpu)
 {
-       WARN_ON_FPU(fpu->fpregs_active);
-
        fpu->fpregs_active = 1;
        this_cpu_write(fpu_fpregs_owner_ctx, fpu);
        trace_x86_fpu_regs_activated(fpu);
@@ -604,8 +600,7 @@ static inline void user_fpu_begin(void)
        struct fpu *fpu = &current->thread.fpu;
 
        preempt_disable();
-       if (!fpu->fpregs_active)
-               fpregs_activate(fpu);
+       fpregs_activate(fpu);
        preempt_enable();
 }
 
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index eab2446..01a47e9 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -426,8 +426,7 @@ void fpu__drop(struct fpu *fpu)
                        asm volatile("1: fwait\n"
                                     "2:\n"
                                     _ASM_EXTABLE(1b, 2b));
-                       if (fpu->fpregs_active)
-                               fpregs_deactivate(fpu);
+                       fpregs_deactivate(fpu);
                }
        } else {
                WARN_ON_FPU(fpu->fpregs_active);