KVM: s390: use hrtimer for clock wakeup from idle - v2
This patch reworks the s390 clock comparator wakeup to hrtimer. The clock
comparator is a per-cpu value that is compared against the TOD clock. If
ckc <= TOD an external interrupt 1004 is triggered. Since the clock comparator
and the TOD clock have a much higher resolution than jiffies we should use
hrtimers to trigger the wakeup. This speeds up guest nanosleep for small
values.
Since hrtimers callbacks run in hard-irq context, I added a tasklet to do
the actual work with enabled interrupts.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Christian Ehrhardt <ehrhardt@de.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 4ed4c3a..a48830f 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -12,6 +12,8 @@
#include <asm/lowcore.h>
#include <asm/uaccess.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
#include <linux/kvm_host.h>
#include <linux/signal.h>
#include "kvm-s390.h"
@@ -361,12 +363,10 @@
return 0;
}
- sltime = (vcpu->arch.sie_block->ckc - now) / (0xf4240000ul / HZ) + 1;
+ sltime = ((vcpu->arch.sie_block->ckc - now)*125)>>9;
- vcpu->arch.ckc_timer.expires = jiffies + sltime;
-
- add_timer(&vcpu->arch.ckc_timer);
- VCPU_EVENT(vcpu, 5, "enabled wait timer:%llx jiffies", sltime);
+ hrtimer_start(&vcpu->arch.ckc_timer, ktime_set (0, sltime) , HRTIMER_MODE_REL);
+ VCPU_EVENT(vcpu, 5, "enabled wait via clock comparator: %llx ns", sltime);
no_timer:
spin_lock_bh(&vcpu->arch.local_int.float_int->lock);
spin_lock_bh(&vcpu->arch.local_int.lock);
@@ -389,21 +389,34 @@
remove_wait_queue(&vcpu->wq, &wait);
spin_unlock_bh(&vcpu->arch.local_int.lock);
spin_unlock_bh(&vcpu->arch.local_int.float_int->lock);
- del_timer(&vcpu->arch.ckc_timer);
+ hrtimer_try_to_cancel(&vcpu->arch.ckc_timer);
return 0;
}
-void kvm_s390_idle_wakeup(unsigned long data)
+void kvm_s390_tasklet(unsigned long parm)
{
- struct kvm_vcpu *vcpu = (struct kvm_vcpu *)data;
+ struct kvm_vcpu *vcpu = (struct kvm_vcpu *) parm;
- spin_lock_bh(&vcpu->arch.local_int.lock);
+ spin_lock(&vcpu->arch.local_int.lock);
vcpu->arch.local_int.timer_due = 1;
if (waitqueue_active(&vcpu->arch.local_int.wq))
wake_up_interruptible(&vcpu->arch.local_int.wq);
- spin_unlock_bh(&vcpu->arch.local_int.lock);
+ spin_unlock(&vcpu->arch.local_int.lock);
}
+/*
+ * low level hrtimer wake routine. Because this runs in hardirq context
+ * we schedule a tasklet to do the real work.
+ */
+enum hrtimer_restart kvm_s390_idle_wakeup(struct hrtimer *timer)
+{
+ struct kvm_vcpu *vcpu;
+
+ vcpu = container_of(timer, struct kvm_vcpu, arch.ckc_timer);
+ tasklet_schedule(&vcpu->arch.tasklet);
+
+ return HRTIMER_NORESTART;
+}
void kvm_s390_deliver_pending_interrupts(struct kvm_vcpu *vcpu)
{