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    Subject[PATCH 19/33] x86/fpu: Decouple fpregs_activate()/fpregs_deactivate() from fpu->fpregs_active
    Date
    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: Andy Lutomirski <luto@kernel.org>
    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: Rik van Riel <riel@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
    Signed-off-by: Ingo Molnar <mingo@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 7fa676f93ac1..42a601673c09 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 eab244622402..01a47e9edfb4 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);
    --
    2.11.0
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