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authorKonstantin Weitz <WEITZKON@de.ibm.com>2012-04-25 15:30:38 +0200
committerMarcelo Tosatti <mtosatti@redhat.com>2012-04-30 21:38:31 -0300
commit41628d334361670d825fb03c04568f5ef9f084dc (patch)
tree88b2eadd0f7de12f1d8b226e4491532b8783ee94 /virt
parentb6ddf05ff68d81a7c1736717faf492b70e9bf4f9 (diff)
KVM: s390: Implement the directed yield (diag 9c) hypervisor call for KVM
This patch implements the directed yield hypercall found on other System z hypervisors. It delegates execution time to the virtual cpu specified in the instruction's parameter. Useful to avoid long spinlock waits in the guest. Christian Borntraeger: moved common code in virt/kvm/ Signed-off-by: Konstantin Weitz <WEITZKON@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c42
1 files changed, 26 insertions, 16 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1847c762d8d..7e140683ff1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1543,6 +1543,31 @@ void kvm_resched(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(kvm_resched);
+bool kvm_vcpu_yield_to(struct kvm_vcpu *target)
+{
+ struct pid *pid;
+ struct task_struct *task = NULL;
+
+ rcu_read_lock();
+ pid = rcu_dereference(target->pid);
+ if (pid)
+ task = get_pid_task(target->pid, PIDTYPE_PID);
+ rcu_read_unlock();
+ if (!task)
+ return false;
+ if (task->flags & PF_VCPU) {
+ put_task_struct(task);
+ return false;
+ }
+ if (yield_to(task, 1)) {
+ put_task_struct(task);
+ return true;
+ }
+ put_task_struct(task);
+ return false;
+}
+EXPORT_SYMBOL_GPL(kvm_vcpu_yield_to);
+
void kvm_vcpu_on_spin(struct kvm_vcpu *me)
{
struct kvm *kvm = me->kvm;
@@ -1561,8 +1586,6 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
*/
for (pass = 0; pass < 2 && !yielded; pass++) {
kvm_for_each_vcpu(i, vcpu, kvm) {
- struct task_struct *task = NULL;
- struct pid *pid;
if (!pass && i < last_boosted_vcpu) {
i = last_boosted_vcpu;
continue;
@@ -1572,24 +1595,11 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
continue;
if (waitqueue_active(&vcpu->wq))
continue;
- rcu_read_lock();
- pid = rcu_dereference(vcpu->pid);
- if (pid)
- task = get_pid_task(vcpu->pid, PIDTYPE_PID);
- rcu_read_unlock();
- if (!task)
- continue;
- if (task->flags & PF_VCPU) {
- put_task_struct(task);
- continue;
- }
- if (yield_to(task, 1)) {
- put_task_struct(task);
+ if (kvm_vcpu_yield_to(vcpu)) {
kvm->last_boosted_vcpu = i;
yielded = 1;
break;
}
- put_task_struct(task);
}
}
}