KVM: i8254: remove notifiers from PIT discard policy

Discard policy doesn't rely on information from notifiers, so we don't
need to register notifiers unconditionally.  We kept correct counts in
case userspace switched between policies during runtime, but that can be
avoided by reseting the state.

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 b8582fbe4fcf30fb9ba9e7d121b6a235fca4f73a..7a2f14bdf4b525d0d225d255df8b72b766bec046 100644 (file)
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -225,7 +225,7 @@ static void kvm_pit_ack_irq(struct kvm_irq_ack_notifier *kian)
         * inc(pending) in pit_timer_fn and xchg(irq_ack, 0) in pit_do_work.
         */
        smp_mb();
-       if (atomic_dec_if_positive(&ps->pending) > 0 && ps->reinject)
+       if (atomic_dec_if_positive(&ps->pending) > 0)
                queue_kthread_work(&ps->pit->worker, &ps->pit->expired);
 }
 
@@ -301,6 +301,27 @@ static inline void kvm_pit_reset_reinject(struct kvm_pit *pit)
        atomic_set(&pit->pit_state.irq_ack, 1);
 }
 
+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)
+               return;
+
+       if (reinject) {
+               /* The initial state is preserved while ps->reinject == 0. */
+               kvm_pit_reset_reinject(pit);
+               kvm_register_irq_ack_notifier(kvm, &ps->irq_ack_notifier);
+               kvm_register_irq_mask_notifier(kvm, 0, &pit->mask_notifier);
+       } else {
+               kvm_unregister_irq_ack_notifier(kvm, &ps->irq_ack_notifier);
+               kvm_unregister_irq_mask_notifier(kvm, 0, &pit->mask_notifier);
+       }
+
+       ps->reinject = reinject;
+}
+
 static void create_pit_timer(struct kvm_pit *pit, u32 val, int is_period)
 {
        struct kvm_kpit_state *ps = &pit->pit_state;
@@ -681,15 +702,14 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
        pit_state = &pit->pit_state;
        pit_state->pit = pit;
        hrtimer_init(&pit_state->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+
        pit_state->irq_ack_notifier.gsi = 0;
        pit_state->irq_ack_notifier.irq_acked = kvm_pit_ack_irq;
-       kvm_register_irq_ack_notifier(kvm, &pit_state->irq_ack_notifier);
-       pit_state->reinject = true;
+       pit->mask_notifier.func = pit_mask_notifer;
 
        kvm_pit_reset(pit);
 
-       pit->mask_notifier.func = pit_mask_notifer;
-       kvm_register_irq_mask_notifier(kvm, 0, &pit->mask_notifier);
+       kvm_pit_set_reinject(pit, true);
 
        kvm_iodevice_init(&pit->dev, &pit_dev_ops);
        ret = kvm_io_bus_register_dev(kvm, KVM_PIO_BUS, KVM_PIT_BASE_ADDRESS,
@@ -712,8 +732,7 @@ fail_unregister:
        kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS, &pit->dev);
 
 fail:
-       kvm_unregister_irq_mask_notifier(kvm, 0, &pit->mask_notifier);
-       kvm_unregister_irq_ack_notifier(kvm, &pit_state->irq_ack_notifier);
+       kvm_pit_set_reinject(pit, false);
        kvm_free_irq_source_id(kvm, pit->irq_source_id);
        kthread_stop(pit->worker_task);
        kfree(pit);
@@ -728,10 +747,7 @@ void kvm_free_pit(struct kvm *kvm)
                kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS, &kvm->arch.vpit->dev);
                kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS,
                                              &kvm->arch.vpit->speaker_dev);
-               kvm_unregister_irq_mask_notifier(kvm, 0,
-                                              &kvm->arch.vpit->mask_notifier);
-               kvm_unregister_irq_ack_notifier(kvm,
-                               &kvm->arch.vpit->pit_state.irq_ack_notifier);
+               kvm_pit_set_reinject(kvm->arch.vpit, false);
                timer = &kvm->arch.vpit->pit_state.timer;
                hrtimer_cancel(timer);
                flush_kthread_work(&kvm->arch.vpit->expired);

diff --git a/arch/x86/kvm/i8254.h b/arch/x86/kvm/i8254.h
index 840fbb3cb626d1c92f2a094d2ac265ca756866e4..1945635904a73d29e17a583d60a8c150bcdb9e78 100644 (file)
--- a/arch/x86/kvm/i8254.h
+++ b/arch/x86/kvm/i8254.h
@@ -63,5 +63,6 @@ void kvm_free_pit(struct kvm *kvm);
 
 void kvm_pit_load_count(struct kvm_pit *pit, int channel, u32 val,
                int hpet_legacy_start);
+void kvm_pit_set_reinject(struct kvm_pit *pit, bool reinject);
 
 #endif

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ce4e91db5bae079b1bd0408e700ce33110990827..76f9f48898a545b1ce539c115b076fd46651ec92 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3659,10 +3659,18 @@ static int kvm_vm_ioctl_set_pit2(struct kvm *kvm, struct kvm_pit_state2 *ps)
 static int kvm_vm_ioctl_reinject(struct kvm *kvm,
                                 struct kvm_reinject_control *control)
 {
-       if (!kvm->arch.vpit)
+       struct kvm_pit *pit = kvm->arch.vpit;
+
+       if (!pit)
                return -ENXIO;
 
-       kvm->arch.vpit->pit_state.reinject = control->pit_reinject;
+       /* pit->pit_state.lock was overloaded to prevent userspace from getting
+        * an inconsistent state after running multiple KVM_REINJECT_CONTROL
+        * ioctls in parallel.  Use a separate lock if that ioctl isn't rare.
+        */
+       mutex_lock(&pit->pit_state.lock);
+       kvm_pit_set_reinject(pit, control->pit_reinject);
+       mutex_unlock(&pit->pit_state.lock);
 
        return 0;
 }