KVM: x86: do not execute halted vcpus

Offline or uninitialized vcpu's can be executed if requested to perform
userspace work.

Follow Avi's suggestion to handle halted vcpu's in the main loop,
simplifying kvm_emulate_halt(). Introduce a new vcpu->requests bit to
indicate events that promote state from halted to running.

Also standardize vcpu wake sites.

Signed-off-by: Marcelo Tosatti <mtosatti <at> redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

5 files changed, 67 insertions, 65 deletions

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 4cb443026ec4..634132a9a512 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -200,10 +200,9 @@ static int __pit_timer_fn(struct kvm_kpit_state *ps)
 
         if (!atomic_inc_and_test(&pt->pending))
                 set_bit(KVM_REQ_PENDING_TIMER, &vcpu0->requests);
-        if (vcpu0 && waitqueue_active(&vcpu0->wq)) {
-                vcpu0->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+
+        if (vcpu0 && waitqueue_active(&vcpu0->wq))
                 wake_up_interruptible(&vcpu0->wq);
-        }
 
         pt->timer.expires = ktime_add_ns(pt->timer.expires, pt->period);
         pt->scheduled = ktime_to_ns(pt->timer.expires);
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index be94f93a73f6..fd00f698692f 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -339,13 +339,7 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
                 } else
                         apic_clear_vector(vector, apic->regs + APIC_TMR);
 
-                if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE)
-                        kvm_vcpu_kick(vcpu);
-                else if (vcpu->arch.mp_state == KVM_MP_STATE_HALTED) {
-                        vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
-                        if (waitqueue_active(&vcpu->wq))
-                                wake_up_interruptible(&vcpu->wq);
-                }
+                kvm_vcpu_kick(vcpu);
 
                 result = (orig_irr == 0);
                 break;
@@ -384,8 +378,7 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
                 if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
                         vcpu->arch.sipi_vector = vector;
                         vcpu->arch.mp_state = KVM_MP_STATE_SIPI_RECEIVED;
-                        if (waitqueue_active(&vcpu->wq))
-                                wake_up_interruptible(&vcpu->wq);
+                        kvm_vcpu_kick(vcpu);
                 }
                 break;
 
@@ -950,10 +943,9 @@ static int __apic_timer_fn(struct kvm_lapic *apic)
 
         if(!atomic_inc_and_test(&apic->timer.pending))
                 set_bit(KVM_REQ_PENDING_TIMER, &apic->vcpu->requests);
-        if (waitqueue_active(q)) {
-                apic->vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+        if (waitqueue_active(q))
                 wake_up_interruptible(q);
-        }
+
         if (apic_lvtt_period(apic)) {
                 result = 1;
                 apic->timer.dev.expires = ktime_add_ns(
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3f3cb7107c03..bf98d40b21ec 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2798,11 +2798,6 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
         KVMTRACE_0D(HLT, vcpu, handler);
         if (irqchip_in_kernel(vcpu->kvm)) {
                 vcpu->arch.mp_state = KVM_MP_STATE_HALTED;
-                up_read(&vcpu->kvm->slots_lock);
-                kvm_vcpu_block(vcpu);
-                down_read(&vcpu->kvm->slots_lock);
-                if (vcpu->arch.mp_state != KVM_MP_STATE_RUNNABLE)
-                        return -EINTR;
                 return 1;
         } else {
                 vcpu->run->exit_reason = KVM_EXIT_HLT;
@@ -3097,24 +3092,10 @@ static void vapic_exit(struct kvm_vcpu *vcpu)
         up_read(&vcpu->kvm->slots_lock);
 }
 
-static int __vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
+static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
         int r;
 
-        if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED)) {
-                pr_debug("vcpu %d received sipi with vector # %x\n",
-                       vcpu->vcpu_id, vcpu->arch.sipi_vector);
-                kvm_lapic_reset(vcpu);
-                r = kvm_x86_ops->vcpu_reset(vcpu);
-                if (r)
-                        return r;
-                vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
-        }
-
-        down_read(&vcpu->kvm->slots_lock);
-        vapic_enter(vcpu);
-
-again:
         if (vcpu->requests)
                 if (test_and_clear_bit(KVM_REQ_MMU_RELOAD, &vcpu->requests))
                         kvm_mmu_unload(vcpu);
@@ -3151,22 +3132,13 @@ again:
 
         local_irq_disable();
 
-        if (vcpu->requests || need_resched()) {
+        if (vcpu->requests || need_resched() || signal_pending(current)) {
                 local_irq_enable();
                 preempt_enable();
                 r = 1;
                 goto out;
         }
 
-        if (signal_pending(current)) {
-                local_irq_enable();
-                preempt_enable();
-                r = -EINTR;
-                kvm_run->exit_reason = KVM_EXIT_INTR;
-                ++vcpu->stat.signal_exits;
-                goto out;
-        }
-
         if (vcpu->guest_debug.enabled)
                 kvm_x86_ops->guest_debug_pre(vcpu);
 
@@ -3227,26 +3199,63 @@ again:
         kvm_lapic_sync_from_vapic(vcpu);
 
         r = kvm_x86_ops->handle_exit(kvm_run, vcpu);
+out:
+        return r;
+}
 
-        if (r > 0) {
-                if (dm_request_for_irq_injection(vcpu, kvm_run)) {
-                        r = -EINTR;
-                        kvm_run->exit_reason = KVM_EXIT_INTR;
-                        ++vcpu->stat.request_irq_exits;
-                        goto out;
-                }
-                if (!need_resched())
-                        goto again;
+static int __vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
+{
+        int r;
+
+        if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED)) {
+                printk("vcpu %d received sipi with vector # %x\n",
+                       vcpu->vcpu_id, vcpu->arch.sipi_vector);
+                kvm_lapic_reset(vcpu);
+                r = kvm_x86_ops->vcpu_reset(vcpu);
+                if (r)
+                        return r;
+                vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
         }
 
-out:
-        up_read(&vcpu->kvm->slots_lock);
-        if (r > 0) {
-                kvm_resched(vcpu);
-                down_read(&vcpu->kvm->slots_lock);
-                goto again;
+        down_read(&vcpu->kvm->slots_lock);
+        vapic_enter(vcpu);
+
+        r = 1;
+        while (r > 0) {
+                if (kvm_arch_vcpu_runnable(vcpu))
+                        r = vcpu_enter_guest(vcpu, kvm_run);
+                else {
+                        up_read(&vcpu->kvm->slots_lock);
+                        kvm_vcpu_block(vcpu);
+                        down_read(&vcpu->kvm->slots_lock);
+                        if (test_and_clear_bit(KVM_REQ_UNHALT, &vcpu->requests))
+                                if (vcpu->arch.mp_state == KVM_MP_STATE_HALTED)
+                                        vcpu->arch.mp_state =
+                                                        KVM_MP_STATE_RUNNABLE;
+                        if (vcpu->arch.mp_state != KVM_MP_STATE_RUNNABLE)
+                                r = -EINTR;
+                }
+
+                if (r > 0) {
+                        if (dm_request_for_irq_injection(vcpu, kvm_run)) {
+                                r = -EINTR;
+                                kvm_run->exit_reason = KVM_EXIT_INTR;
+                                ++vcpu->stat.request_irq_exits;
+                        }
+                        if (signal_pending(current)) {
+                                r = -EINTR;
+                                kvm_run->exit_reason = KVM_EXIT_INTR;
+                                ++vcpu->stat.signal_exits;
+                        }
+                        if (need_resched()) {
+                                up_read(&vcpu->kvm->slots_lock);
+                                kvm_resched(vcpu);
+                                down_read(&vcpu->kvm->slots_lock);
+                        }
+                }
         }
 
+        up_read(&vcpu->kvm->slots_lock);
         post_kvm_run_save(vcpu, kvm_run);
 
         vapic_exit(vcpu);
@@ -3266,6 +3275,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
         if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
                 kvm_vcpu_block(vcpu);
+                clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
                 r = -EAGAIN;
                 goto out;
         }
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a18aaad2ab79..4b036430ea23 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -34,6 +34,7 @@
 #define KVM_REQ_MMU_RELOAD         3
 #define KVM_REQ_TRIPLE_FAULT       4
 #define KVM_REQ_PENDING_TIMER      5
+#define KVM_REQ_UNHALT             6
 
 struct kvm_vcpu;
 extern struct kmem_cache *kvm_vcpu_cache;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index de3b029f6adf..63e661be040a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -980,12 +980,12 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
         for (;;) {
                 prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
 
-                if (kvm_cpu_has_interrupt(vcpu))
-                        break;
-                if (kvm_cpu_has_pending_timer(vcpu))
-                        break;
-                if (kvm_arch_vcpu_runnable(vcpu))
+                if (kvm_cpu_has_interrupt(vcpu) ||
+                    kvm_cpu_has_pending_timer(vcpu) ||
+                    kvm_arch_vcpu_runnable(vcpu)) {
+                        set_bit(KVM_REQ_UNHALT, &vcpu->requests);
                         break;
+                }
                 if (signal_pending(current))
                         break;