KVM: i8254: turn kvm_kpit_state.reinject into atomic_t

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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 68af4445d51d18c4c8120d34418c8648bc09d323..219ef855aae508dc9353de3e3071c130f4a3e95f 100644 (file)
--- 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 f365dce4fb8d5c863caf19cad7e8cafb556b0b25..2f5af079832694e40baba94d41208a85511d04bd 100644 (file)
--- 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;