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KVM: s390: use hrtimer for clock wakeup from idle - v2

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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>
This commit is contained in:
Christian Borntraeger
2009-05-12 17:21:49 +02:00
committed by Avi Kivity
parent 2668dab794
commit ca8723023f
4 changed files with 35 additions and 14 deletions
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33
arch/s390/kvm/interrupt.c
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@@ -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 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
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 @@ no_timer:
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)
{