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    Subject[RFC PATCH 07/11] x86,fpu: store current fpu pointer, instead of fpu_owner_task
    Date
    From: Rik van Riel <riel@redhat.com>

    This change has no impact on normal tasks, but it allows tasks
    with multiple FPU states(like a KVM vcpu thread) to check
    whether its other FPU state is still loaded.

    Exported so KVM can use it.

    Signed-off-by: Rik van Riel <riel@redhat.com>
    ---
    arch/x86/include/asm/fpu-internal.h | 15 ++++++++-------
    arch/x86/kernel/cpu/common.c | 5 +++--
    arch/x86/kernel/i387.c | 2 +-
    3 files changed, 12 insertions(+), 10 deletions(-)

    diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
    index a5a40c7..8546c0a 100644
    --- a/arch/x86/include/asm/fpu-internal.h
    +++ b/arch/x86/include/asm/fpu-internal.h
    @@ -42,7 +42,7 @@ extern unsigned int mxcsr_feature_mask;
    extern void fpu_init(void);
    extern void eager_fpu_init(void);

    -DECLARE_PER_CPU(struct task_struct *, fpu_owner_task);
    +DECLARE_PER_CPU(struct fpu *, fpu_owner);

    extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
    struct task_struct *tsk);
    @@ -318,14 +318,14 @@ static inline int __thread_has_fpu(struct task_struct *tsk)
    static inline void __thread_clear_has_fpu(struct task_struct *tsk)
    {
    tsk->thread.fpu.has_fpu = 0;
    - this_cpu_write(fpu_owner_task, NULL);
    + this_cpu_write(fpu_owner, NULL);
    }

    /* Must be paired with a 'clts' before! */
    static inline void __thread_set_has_fpu(struct task_struct *tsk)
    {
    tsk->thread.fpu.has_fpu = 1;
    - this_cpu_write(fpu_owner_task, tsk);
    + this_cpu_write(fpu_owner, &tsk->thread.fpu);
    }

    /*
    @@ -394,13 +394,14 @@ static inline void drop_init_fpu(struct task_struct *tsk)
    */
    static inline void __cpu_disable_lazy_restore(unsigned int cpu)
    {
    - per_cpu(fpu_owner_task, cpu) = NULL;
    + per_cpu(fpu_owner, cpu) = NULL;
    }

    static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)
    {
    - return new == this_cpu_read_stable(fpu_owner_task) &&
    - cpu == new->thread.fpu.last_cpu;
    + struct fpu *new_fpu = &new->thread.fpu;
    + return new_fpu == this_cpu_read_stable(fpu_owner) &&
    + cpu == new_fpu->last_cpu;
    }

    static inline void switch_fpu_prepare(struct task_struct *old, struct task_struct *new, int cpu)
    @@ -421,7 +422,7 @@ static inline void switch_fpu_prepare(struct task_struct *old, struct task_struc
    cpu = ~0;

    old->thread.fpu.last_cpu = cpu;
    - old->thread.fpu.has_fpu = 0; /* But leave fpu_owner_task! */
    + old->thread.fpu.has_fpu = 0; /* But leave fpu_owner! */

    /* Don't change CR0.TS if we just switch! */
    if (preload) {
    diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
    index 36837bb..ad4d1a9 100644
    --- a/arch/x86/kernel/cpu/common.c
    +++ b/arch/x86/kernel/cpu/common.c
    @@ -1143,8 +1143,9 @@ DEFINE_PER_CPU(unsigned int, irq_count) __visible = -1;
    DEFINE_PER_CPU(int, __preempt_count) = INIT_PREEMPT_COUNT;
    EXPORT_PER_CPU_SYMBOL(__preempt_count);

    -/* Task that currently has its FPU state loaded on the CPU. */
    -DEFINE_PER_CPU(struct task_struct *, fpu_owner_task);
    +/* FPU state that is currently loaded on the CPU. */
    +DEFINE_PER_CPU(struct fpu *, fpu_owner);
    +EXPORT_PER_CPU_SYMBOL_GPL(fpu_owner);

    /*
    * Special IST stacks which the CPU switches to when it calls
    diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
    index a9a4229..c98f88d 100644
    --- a/arch/x86/kernel/i387.c
    +++ b/arch/x86/kernel/i387.c
    @@ -78,7 +78,7 @@ void __kernel_fpu_begin(void)
    __save_init_fpu(me);
    /* We do 'stts()' in __kernel_fpu_end() */
    } else if (!use_eager_fpu()) {
    - this_cpu_write(fpu_owner_task, NULL);
    + this_cpu_write(fpu_owner, NULL);
    clts();
    }
    }
    --
    1.9.3


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