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KVM: s390: Implement the directed yield (diag 9c) hypervisor call for KVM

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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>
This commit is contained in:
Konstantin Weitz
2012-04-25 15:30:38 +02:00
committed by Marcelo Tosatti
parent b6ddf05ff6
commit 41628d3343
5 changed files with 54 additions and 16 deletions
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virt/kvm/kvm_main.c
+26 -16
View File
@@ -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);
}
}
}