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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>
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Konstantin Weitz Marcelo Tosatti
Konstantin Weitz authored and Marcelo Tosatti committed Apr 25, 2012
1 parent b6ddf05 commit 41628d334361670d825fb03c04568f5ef9f084dc
Showing with 54 additions and 16 deletions.
  1. +1 −0 arch/s390/include/asm/kvm_host.h
  2. +25 −0 arch/s390/kvm/diag.c
  3. +1 −0 arch/s390/kvm/kvm-s390.c
  4. +1 −0 include/linux/kvm_host.h
  5. +26 −16 virt/kvm/kvm_main.c
@@ -148,6 +148,7 @@ struct kvm_vcpu_stat {
u32 instruction_sigp_restart;
u32 diagnose_10;
u32 diagnose_44;
u32 diagnose_9c;
};
struct kvm_s390_io_info {
View
@@ -53,6 +53,29 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
return 0;
}
static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu)
{
struct kvm *kvm = vcpu->kvm;
struct kvm_vcpu *tcpu;
int tid;
int i;
tid = vcpu->run->s.regs.gprs[(vcpu->arch.sie_block->ipa & 0xf0) >> 4];
vcpu->stat.diagnose_9c++;
VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d", tid);
if (tid == vcpu->vcpu_id)
return 0;
kvm_for_each_vcpu(i, tcpu, kvm)
if (tcpu->vcpu_id == tid) {
kvm_vcpu_yield_to(tcpu);
break;
}
return 0;
}
static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
{
unsigned int reg = vcpu->arch.sie_block->ipa & 0xf;
@@ -89,6 +112,8 @@ int kvm_s390_handle_diag(struct kvm_vcpu *vcpu)
return diag_release_pages(vcpu);
case 0x44:
return __diag_time_slice_end(vcpu);
case 0x9c:
return __diag_time_slice_end_directed(vcpu);
case 0x308:
return __diag_ipl_functions(vcpu);
default:
View
@@ -74,6 +74,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "instruction_sigp_restart", VCPU_STAT(instruction_sigp_restart) },
{ "diagnose_10", VCPU_STAT(diagnose_10) },
{ "diagnose_44", VCPU_STAT(diagnose_44) },
{ "diagnose_9c", VCPU_STAT(diagnose_9c) },
{ NULL }
};
View
@@ -461,6 +461,7 @@ void mark_page_dirty_in_slot(struct kvm *kvm, struct kvm_memory_slot *memslot,
void kvm_vcpu_block(struct kvm_vcpu *vcpu);
void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
bool kvm_vcpu_yield_to(struct kvm_vcpu *target);
void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
void kvm_resched(struct kvm_vcpu *vcpu);
void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
View
@@ -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);
}
}
}

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