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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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5
arch/s390/include/asm/kvm_host.h
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@ -13,6 +13,8 @@
#ifndef ASM_KVM_HOST_H
#define ASM_KVM_HOST_H
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/kvm_host.h>
#include <asm/debug.h>
#include <asm/cpuid.h>
@ -210,7 +212,8 @@ struct kvm_vcpu_arch {
s390_fp_regs guest_fpregs;
unsigned int guest_acrs[NUM_ACRS];
struct kvm_s390_local_interrupt local_int;
struct timer_list ckc_timer;
struct hrtimer ckc_timer;
struct tasklet_struct tasklet;
union {
cpuid_t cpu_id;
u64 stidp_data;

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 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
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)
{

7
arch/s390/kvm/kvm-s390.c
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@ -15,6 +15,7 @@
#include <linux/compiler.h>
#include <linux/err.h>
#include <linux/fs.h>
#include <linux/hrtimer.h>
#include <linux/init.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
@ -283,8 +284,10 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
vcpu->arch.sie_block->gmsor = vcpu->kvm->arch.guest_origin;
vcpu->arch.sie_block->ecb = 2;
vcpu->arch.sie_block->eca = 0xC1002001U;
setup_timer(&vcpu->arch.ckc_timer, kvm_s390_idle_wakeup,
(unsigned long) vcpu);
hrtimer_init(&vcpu->arch.ckc_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
tasklet_init(&vcpu->arch.tasklet, kvm_s390_tasklet,
(unsigned long) vcpu);
vcpu->arch.ckc_timer.function = kvm_s390_idle_wakeup;
get_cpu_id(&vcpu->arch.cpu_id);
vcpu->arch.cpu_id.version = 0xff;
return 0;

4
arch/s390/kvm/kvm-s390.h
View File

@ -14,6 +14,7 @@
#ifndef ARCH_S390_KVM_S390_H
#define ARCH_S390_KVM_S390_H
#include <linux/hrtimer.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
@ -41,7 +42,8 @@ static inline int __cpu_is_stopped(struct kvm_vcpu *vcpu)
}
int kvm_s390_handle_wait(struct kvm_vcpu *vcpu);
void kvm_s390_idle_wakeup(unsigned long data);
enum hrtimer_restart kvm_s390_idle_wakeup(struct hrtimer *timer);
void kvm_s390_tasklet(unsigned long parm);
void kvm_s390_deliver_pending_interrupts(struct kvm_vcpu *vcpu);
int kvm_s390_inject_vm(struct kvm *kvm,
struct kvm_s390_interrupt *s390int);