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    Subject[PATCH 2/7] x86/fpu: Simplify fpu->fpregs_active use
    Date
    The fpregs_active() inline function is pretty pointless - in almost
    all the callsites it can be replaced with a direct fpu->fpregs_active
    access.

    Do so and eliminate the extra layer of obfuscation.

    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 | 17 +----------------
    arch/x86/kernel/fpu/core.c | 2 +-
    arch/x86/kernel/fpu/signal.c | 9 +++++----
    arch/x86/mm/pkeys.c | 2 +-
    drivers/lguest/x86/core.c | 2 +-
    5 files changed, 9 insertions(+), 23 deletions(-)

    diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
    index 2eaf93cf11cc..d6307e76837c 100644
    --- a/arch/x86/include/asm/fpu/internal.h
    +++ b/arch/x86/include/asm/fpu/internal.h
    @@ -543,21 +543,6 @@ static inline void fpregs_activate(struct fpu *fpu)
    }

    /*
    - * The question "does this thread have fpu access?"
    - * is slightly racy, since preemption could come in
    - * and revoke it immediately after the test.
    - *
    - * However, even in that very unlikely scenario,
    - * we can just assume we have FPU access - typically
    - * to save the FP state - we'll just take a #NM
    - * fault and get the FPU access back.
    - */
    -static inline int fpregs_active(void)
    -{
    - return current->thread.fpu.fpregs_active;
    -}
    -
    -/*
    * FPU state switching for scheduling.
    *
    * This is a two-stage process:
    @@ -618,7 +603,7 @@ static inline void user_fpu_begin(void)
    struct fpu *fpu = &current->thread.fpu;

    preempt_disable();
    - if (!fpregs_active())
    + if (!fpu->fpregs_active)
    fpregs_activate(fpu);
    preempt_enable();
    }
    diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
    index 287f1cb32b59..8775343ca75b 100644
    --- a/arch/x86/kernel/fpu/core.c
    +++ b/arch/x86/kernel/fpu/core.c
    @@ -367,7 +367,7 @@ void fpu__current_fpstate_write_end(void)
    * registers may still be out of date. Update them with
    * an XRSTOR if they are active.
    */
    - if (fpregs_active())
    + if (fpu->fpregs_active)
    copy_kernel_to_fpregs(&fpu->state);

    /*
    diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
    index 2d682dac35d4..684025654d0c 100644
    --- a/arch/x86/kernel/fpu/signal.c
    +++ b/arch/x86/kernel/fpu/signal.c
    @@ -155,7 +155,8 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
    */
    int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
    {
    - struct xregs_state *xsave = &current->thread.fpu.state.xsave;
    + struct fpu *fpu = &current->thread.fpu;
    + struct xregs_state *xsave = &fpu->state.xsave;
    struct task_struct *tsk = current;
    int ia32_fxstate = (buf != buf_fx);

    @@ -170,13 +171,13 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
    sizeof(struct user_i387_ia32_struct), NULL,
    (struct _fpstate_32 __user *) buf) ? -1 : 1;

    - if (fpregs_active() || using_compacted_format()) {
    + if (fpu->fpregs_active || using_compacted_format()) {
    /* Save the live register state to the user directly. */
    if (copy_fpregs_to_sigframe(buf_fx))
    return -1;
    /* Update the thread's fxstate to save the fsave header. */
    if (ia32_fxstate)
    - copy_fxregs_to_kernel(&tsk->thread.fpu);
    + copy_fxregs_to_kernel(fpu);
    } else {
    /*
    * It is a *bug* if kernel uses compacted-format for xsave
    @@ -189,7 +190,7 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
    return -1;
    }

    - fpstate_sanitize_xstate(&tsk->thread.fpu);
    + fpstate_sanitize_xstate(fpu);
    if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size))
    return -1;
    }
    diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
    index 2dab69a706ec..e2c23472233e 100644
    --- a/arch/x86/mm/pkeys.c
    +++ b/arch/x86/mm/pkeys.c
    @@ -45,7 +45,7 @@ int __execute_only_pkey(struct mm_struct *mm)
    */
    preempt_disable();
    if (!need_to_set_mm_pkey &&
    - fpregs_active() &&
    + current->thread.fpu.fpregs_active &&
    !__pkru_allows_read(read_pkru(), execute_only_pkey)) {
    preempt_enable();
    return execute_only_pkey;
    diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
    index d71f6323ac00..328974ae690d 100644
    --- a/drivers/lguest/x86/core.c
    +++ b/drivers/lguest/x86/core.c
    @@ -289,7 +289,7 @@ void lguest_arch_run_guest(struct lg_cpu *cpu)
    * a different CPU. So all the critical stuff should be done
    * before this.
    */
    - else if (cpu->regs->trapnum == 7 && !fpregs_active())
    + else if (cpu->regs->trapnum == 7 && !current->thread.fpu.fpstate_active)
    fpu__restore(&current->thread.fpu);
    }

    --
    2.7.4
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