From: Konstantin Weitz <WEITZKON@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
arch/s390/include/asm/kvm_host.h | 1 +
arch/s390/kvm/diag.c | 25 +++++++++++++++++++++++
arch/s390/kvm/kvm-s390.c | 1 +
include/linux/kvm_host.h | 1 +
virt/kvm/kvm_main.c | 42 +++++++++++++++++++++++---------------
5 files changed, 54 insertions(+), 16 deletions(-)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 7343872..dd17537 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -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 {
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index a353f0e..2d2ae32 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -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:
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 044ca7e..0054cb0 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -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 }
};
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 186ffab..2322b21 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -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);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9eb7936..99a38a4 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);
}
}
}
--
1.7.9.6
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