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Commit ca872302 authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Avi Kivity
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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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarCarsten Otte <cotte@de.ibm.com>
Signed-off-by: default avatarChristian Ehrhardt <ehrhardt@de.ibm.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 2668dab7

arch/s390/include/asm/kvm_host.h

+4 −1
Original line number Diff line number Diff line
@@ -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;

arch/s390/kvm/interrupt.c

+23 −10
Original line number Diff line number Diff line
@@ -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)

{

arch/s390/kvm/kvm-s390.c

+5 −2
Original line number Diff line number Diff line
@@ -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,

	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;

arch/s390/kvm/kvm-s390.h

+3 −1
Original line number Diff line number Diff line
@@ -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);