[PATCH 27/27] Use hrtimers for the decrementer

Alexander Graf
2009-10-21T15:03:33Z

Following S390's good example we should use hrtimers for the decrementer too!
This patch converts the timer from the old mechanism to hrtimers.

Signed-off-by: Alexander Graf <agraf-l3A5Bk7waGM@public.gmane.org>
---
arch/powerpc/include/asm/kvm_host.h | 6 ++++--
arch/powerpc/kvm/emulate.c | 18 +++++++++++-------
arch/powerpc/kvm/powerpc.c | 20 ++++++++++++++++++--
3 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 2cff5fe..1201f62 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -21,7 +21,8 @@
#define __POWERPC_KVM_HOST_H__

#include <linux/mutex.h>
-#include <linux/timer.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
#include <linux/types.h>
#include <linux/kvm_types.h>
#include <asm/kvm_asm.h>
@@ -250,7 +251,8 @@ struct kvm_vcpu_arch {

u32 cpr0_cfgaddr; /* holds the last set cpr0_cfgaddr */

- struct timer_list dec_timer;
+ struct hrtimer dec_timer;
+ struct tasklet_struct tasklet;
u64 dec_jiffies;
unsigned long pending_exceptions;

diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
index 1ec5e07..4a9ac66 100644
--- a/arch/powerpc/kvm/emulate.c
+++ b/arch/powerpc/kvm/emulate.c
@@ -18,7 +18,7 @@
*/

#include <linux/jiffies.h>
-#include <linux/timer.h>
+#include <linux/hrtimer.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/kvm_host.h>
@@ -79,12 +79,13 @@ static int kvmppc_dec_enabled(struct kvm_vcpu *vcpu)

void kvmppc_emulate_dec(struct kvm_vcpu *vcpu)
{
- unsigned long nr_jiffies;
+ unsigned long dec_nsec;

+ pr_debug("mtDEC: %x\n", vcpu->arch.dec);
#ifdef CONFIG_PPC64
/* POWER4+ triggers a dec interrupt if the value is < 0 */
if (vcpu->arch.dec & 0x80000000) {
- del_timer(&vcpu->arch.dec_timer);
+ hrtimer_try_to_cancel(&vcpu->arch.dec_timer);
kvmppc_core_queue_dec(vcpu);
return;
}
@@ -94,12 +95,15 @@ void kvmppc_emulate_dec(struct kvm_vcpu *vcpu)
* that's how we convert the guest DEC value to the number of
* host ticks. */

+ hrtimer_try_to_cancel(&vcpu->arch.dec_timer);
+ dec_nsec = vcpu->arch.dec;
+ dec_nsec *= 1000;
+ dec_nsec /= tb_ticks_per_usec;
+ hrtimer_start(&vcpu->arch.dec_timer, ktime_set(0, dec_nsec),
+ HRTIMER_MODE_REL);
vcpu->arch.dec_jiffies = get_tb();
- nr_jiffies = vcpu->arch.dec / tb_ticks_per_jiffy;
- mod_timer(&vcpu->arch.dec_timer,
- get_jiffies_64() + nr_jiffies);
} else {
- del_timer(&vcpu->arch.dec_timer);
+ hrtimer_try_to_cancel(&vcpu->arch.dec_timer);
}
}

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 4ae3490..4c582ed 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -23,6 +23,7 @@
#include <linux/kvm_host.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
+#include <linux/hrtimer.h>
#include <linux/fs.h>
#include <asm/cputable.h>
#include <asm/uaccess.h>
@@ -209,10 +210,25 @@ static void kvmppc_decrementer_func(unsigned long data)
}
}

+/*
+ * low level hrtimer wake routine. Because this runs in hardirq context
+ * we schedule a tasklet to do the real work.
+ */
+enum hrtimer_restart kvmppc_decrementer_wakeup(struct hrtimer *timer)
+{
+ struct kvm_vcpu *vcpu;
+
+ vcpu = container_of(timer, struct kvm_vcpu, arch.dec_timer);
+ tasklet_schedule(&vcpu->arch.tasklet);
+
+ return HRTIMER_NORESTART;
+}
+
int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
{
- setup_timer(&vcpu->arch.dec_timer, kvmppc_decrementer_func,
- (unsigned long)vcpu);
+ hrtimer_init(&vcpu->arch.dec_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
+ tasklet_init(&vcpu->arch.tasklet, kvmppc_decrementer_func, (ulong)vcpu);
+ vcpu->arch.dec_timer.function = kvmppc_decrementer_wakeup;

return 0;
}
--
1.6.0.2