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Diffstat (limited to 'arch/s390/kvm/diag.c')
-rw-r--r--arch/s390/kvm/diag.c31
1 files changed, 28 insertions, 3 deletions
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 5b8ec1c447e1..02c146f9e5cd 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -150,6 +150,19 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
return 0;
}
+static int forward_cnt;
+static unsigned long cur_slice;
+
+static int diag9c_forwarding_overrun(void)
+{
+ /* Reset the count on a new slice */
+ if (time_after(jiffies, cur_slice)) {
+ cur_slice = jiffies;
+ forward_cnt = diag9c_forwarding_hz / HZ;
+ }
+ return forward_cnt-- <= 0 ? 1 : 0;
+}
+
static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu)
{
struct kvm_vcpu *tcpu;
@@ -167,9 +180,21 @@ static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu)
if (!tcpu)
goto no_yield;
- /* target already running */
- if (READ_ONCE(tcpu->cpu) >= 0)
- goto no_yield;
+ /* target guest VCPU already running */
+ if (READ_ONCE(tcpu->cpu) >= 0) {
+ if (!diag9c_forwarding_hz || diag9c_forwarding_overrun())
+ goto no_yield;
+
+ /* target host CPU already running */
+ if (!vcpu_is_preempted(tcpu->cpu))
+ goto no_yield;
+ smp_yield_cpu(tcpu->cpu);
+ VCPU_EVENT(vcpu, 5,
+ "diag time slice end directed to %d: yield forwarded",
+ tid);
+ vcpu->stat.diagnose_9c_forward++;
+ return 0;
+ }
if (kvm_vcpu_yield_to(tcpu) <= 0)
goto no_yield;