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    Subject[PATCH v3 15/16] KVM: x86: turn kvm_kpit_state.reinject into atomic_t
    Date
    From: Radim Krčmář <rkrcmar@redhat.com>

    Document possible races between readers and concurrent update to the
    ioctl.

    Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
    ---
    v3: new

    arch/x86/kvm/i8254.c | 8 ++++----
    arch/x86/kvm/i8254.h | 2 +-
    2 files changed, 5 insertions(+), 5 deletions(-)

    diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
    index 68af4445d51d..219ef855aae5 100644
    --- a/arch/x86/kvm/i8254.c
    +++ b/arch/x86/kvm/i8254.c
    @@ -264,7 +264,7 @@ static void pit_do_work(struct kthread_work *work)
    int i;
    struct kvm_kpit_state *ps = &pit->pit_state;

    - if (ps->reinject && !atomic_xchg(&ps->irq_ack, 0))
    + if (atomic_read(&ps->reinject) && !atomic_xchg(&ps->irq_ack, 0))
    return;

    kvm_set_irq(kvm, pit->irq_source_id, 0, 1, false);
    @@ -289,7 +289,7 @@ static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
    struct kvm_kpit_state *ps = container_of(data, struct kvm_kpit_state, timer);
    struct kvm_pit *pt = pit_state_to_pit(ps);

    - if (ps->reinject)
    + if (atomic_read(&ps->reinject))
    atomic_inc(&ps->pending);

    queue_kthread_work(&pt->worker, &pt->expired);
    @@ -312,7 +312,7 @@ void kvm_pit_set_reinject(struct kvm_pit *pit, bool reinject)
    struct kvm_kpit_state *ps = &pit->pit_state;
    struct kvm *kvm = pit->kvm;

    - if (ps->reinject == reinject)
    + if (atomic_read(&ps->reinject) == reinject)
    return;

    if (reinject) {
    @@ -325,7 +325,7 @@ void kvm_pit_set_reinject(struct kvm_pit *pit, bool reinject)
    kvm_unregister_irq_mask_notifier(kvm, 0, &pit->mask_notifier);
    }

    - ps->reinject = reinject;
    + atomic_set(&ps->reinject, reinject);
    }

    static void create_pit_timer(struct kvm_pit *pit, u32 val, int is_period)
    diff --git a/arch/x86/kvm/i8254.h b/arch/x86/kvm/i8254.h
    index f365dce4fb8d..2f5af0798326 100644
    --- a/arch/x86/kvm/i8254.h
    +++ b/arch/x86/kvm/i8254.h
    @@ -31,7 +31,7 @@ struct kvm_kpit_state {
    u32 speaker_data_on;

    struct mutex lock;
    - bool reinject;
    + atomic_t reinject;
    atomic_t pending; /* accumulated triggered timers */
    atomic_t irq_ack;
    struct kvm_irq_ack_notifier irq_ack_notifier;
    --
    2.7.2
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