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>

1 files changed, 4 insertions, 4 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)