KVM: s390: move vcpu wakeup code to a central point

Let's move the vcpu wakeup code to a central point.

We should set the vcpu->preempted flag only if the target is actually sleeping
and before the real wakeup happens. Otherwise the preempted flag might be set,
when not necessary. This may result in immediate reschedules after schedule()
in some scenarios.

The wakeup code doesn't require the local_int.lock to be held.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 86575b4cdc1c48860cf14942ad54e95a300fbe85..65396e14ff0582a9be99165ee344b8eb51b6e952 100644 (file)
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -617,12 +617,22 @@ no_timer:
        return 0;
 }
 
+void kvm_s390_vcpu_wakeup(struct kvm_vcpu *vcpu)
+{
+       if (waitqueue_active(&vcpu->wq)) {
+               /*
+                * The vcpu gave up the cpu voluntarily, mark it as a good
+                * yield-candidate.
+                */
+               vcpu->preempted = true;
+               wake_up_interruptible(&vcpu->wq);
+       }
+}
+
 void kvm_s390_tasklet(unsigned long parm)
 {
        struct kvm_vcpu *vcpu = (struct kvm_vcpu *) parm;
-
-       if (waitqueue_active(&vcpu->wq))
-               wake_up_interruptible(&vcpu->wq);
+       kvm_s390_vcpu_wakeup(vcpu);
 }
 
 /*
@@ -905,10 +915,8 @@ static int __inject_vm(struct kvm *kvm, struct kvm_s390_interrupt_info *inti)
        li = &dst_vcpu->arch.local_int;
        spin_lock(&li->lock);
        atomic_set_mask(CPUSTAT_EXT_INT, li->cpuflags);
-       if (waitqueue_active(li->wq))
-               wake_up_interruptible(li->wq);
-       kvm_get_vcpu(kvm, sigcpu)->preempted = true;
        spin_unlock(&li->lock);
+       kvm_s390_vcpu_wakeup(kvm_get_vcpu(kvm, sigcpu));
 unlock_fi:
        spin_unlock(&fi->lock);
        mutex_unlock(&kvm->lock);
@@ -1059,11 +1067,9 @@ int kvm_s390_inject_vcpu(struct kvm_vcpu *vcpu,
        if (inti->type == KVM_S390_SIGP_STOP)
                li->action_bits |= ACTION_STOP_ON_STOP;
        atomic_set_mask(CPUSTAT_EXT_INT, li->cpuflags);
-       if (waitqueue_active(&vcpu->wq))
-               wake_up_interruptible(&vcpu->wq);
-       vcpu->preempted = true;
        spin_unlock(&li->lock);
        mutex_unlock(&vcpu->kvm->lock);
+       kvm_s390_vcpu_wakeup(vcpu);
        return 0;
 }
 

diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 33a0e4bed2a5f1ec83331147a218308a6679865c..665eaccb9ca57e7d0b2b423d09fe058598c2d41e 100644 (file)
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -136,6 +136,7 @@ static inline int kvm_s390_user_cpu_state_ctrl(struct kvm *kvm)
 }
 
 int kvm_s390_handle_wait(struct kvm_vcpu *vcpu);
+void kvm_s390_vcpu_wakeup(struct kvm_vcpu *vcpu);
 enum hrtimer_restart kvm_s390_idle_wakeup(struct hrtimer *timer);
 void kvm_s390_tasklet(unsigned long parm);
 void kvm_s390_deliver_pending_interrupts(struct kvm_vcpu *vcpu);

diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
index 946992f7bb252276392e7d36945402f4bdf73f58..c6f1c2bc9753919f1dc87df96d2f263db297a4d1 100644 (file)
--- a/arch/s390/kvm/sigp.c
+++ b/arch/s390/kvm/sigp.c
@@ -125,8 +125,9 @@ static int __sigp_external_call(struct kvm_vcpu *vcpu, u16 cpu_addr)
        return rc ? rc : SIGP_CC_ORDER_CODE_ACCEPTED;
 }
 
-static int __inject_sigp_stop(struct kvm_s390_local_interrupt *li, int action)
+static int __inject_sigp_stop(struct kvm_vcpu *dst_vcpu, int action)
 {
+       struct kvm_s390_local_interrupt *li = &dst_vcpu->arch.local_int;
        struct kvm_s390_interrupt_info *inti;
        int rc = SIGP_CC_ORDER_CODE_ACCEPTED;
 
@@ -151,8 +152,7 @@ static int __inject_sigp_stop(struct kvm_s390_local_interrupt *li, int action)
        atomic_set(&li->active, 1);
        li->action_bits |= action;
        atomic_set_mask(CPUSTAT_STOP_INT, li->cpuflags);
-       if (waitqueue_active(li->wq))
-               wake_up_interruptible(li->wq);
+       kvm_s390_vcpu_wakeup(dst_vcpu);
 out:
        spin_unlock(&li->lock);
 
@@ -161,7 +161,6 @@ out:
 
 static int __sigp_stop(struct kvm_vcpu *vcpu, u16 cpu_addr, int action)
 {
-       struct kvm_s390_local_interrupt *li;
        struct kvm_vcpu *dst_vcpu = NULL;
        int rc;
 
@@ -171,9 +170,8 @@ static int __sigp_stop(struct kvm_vcpu *vcpu, u16 cpu_addr, int action)
        dst_vcpu = kvm_get_vcpu(vcpu->kvm, cpu_addr);
        if (!dst_vcpu)
                return SIGP_CC_NOT_OPERATIONAL;
-       li = &dst_vcpu->arch.local_int;
 
-       rc = __inject_sigp_stop(li, action);
+       rc = __inject_sigp_stop(dst_vcpu, action);
 
        VCPU_EVENT(vcpu, 4, "sent sigp stop to cpu %x", cpu_addr);
 
@@ -258,8 +256,7 @@ static int __sigp_set_prefix(struct kvm_vcpu *vcpu, u16 cpu_addr, u32 address,
 
        list_add_tail(&inti->list, &li->list);
        atomic_set(&li->active, 1);
-       if (waitqueue_active(li->wq))
-               wake_up_interruptible(li->wq);
+       kvm_s390_vcpu_wakeup(dst_vcpu);
        rc = SIGP_CC_ORDER_CODE_ACCEPTED;
 
        VCPU_EVENT(vcpu, 4, "set prefix of cpu %02x to %x", cpu_addr, address);
@@ -466,12 +463,7 @@ int kvm_s390_handle_sigp_pei(struct kvm_vcpu *vcpu)
                dest_vcpu = kvm_get_vcpu(vcpu->kvm, cpu_addr);
                BUG_ON(dest_vcpu == NULL);
 
-               spin_lock(&dest_vcpu->arch.local_int.lock);
-               if (waitqueue_active(&dest_vcpu->wq))
-                       wake_up_interruptible(&dest_vcpu->wq);
-               dest_vcpu->preempted = true;
-               spin_unlock(&dest_vcpu->arch.local_int.lock);
-
+               kvm_s390_vcpu_wakeup(dest_vcpu);
                kvm_s390_set_psw_cc(vcpu, SIGP_CC_ORDER_CODE_ACCEPTED);
                return 0;
        }