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.
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 | 44 ++++++++++++++++++++++++++++++++++++++
arch/s390/kvm/kvm-s390.c | 1 +
3 files changed, 46 insertions(+)
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..8991009 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -53,6 +53,48 @@ 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) {
+ struct task_struct *task = NULL;
+ struct pid *pid;
+ rcu_read_lock();
+ pid = rcu_dereference(tcpu->pid);
+ if (pid)
+ task = get_pid_task(tcpu->pid, PIDTYPE_PID);
+ rcu_read_unlock();
+ if (!task)
+ break;
+ if (task->flags & PF_VCPU) {
+ put_task_struct(task);
+ break;
+ }
+ vcpu_put(vcpu);
+ if (yield_to(task, 1)) {
+ vcpu_load(vcpu);
+ put_task_struct(task);
+ return 0;
+ }
+ vcpu_load(vcpu);
+ put_task_struct(task);
+ }
+ }
+ return 0;
+}
+
static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
{
unsigned int reg = vcpu->arch.sie_block->ipa & 0xf;
@@ -89,6 +131,8 @@ 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 d30c835..fd98914 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 }
};
--
1.7.9.6
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