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Date: Wed, 26 Feb 2014 19:15:12 +0100
From: Andrew Jones <drjones@...hat.com>
To: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: mtosatti@...hat.com, pbonzini@...hat.com
Subject: [PATCH 2/2] x86: kvm: introduce periodic global clock updates
commit 0061d53daf26f introduced a mechanism to execute a global clock
update for a vm. We can apply this periodically in order to propagate
host NTP corrections. Also, if all vcpus of a vm are pinned, then
without an additional trigger, no guest NTP corrections can propagate
either, as the current trigger is only vcpu cpu migration.
Signed-off-by: Andrew Jones <drjones@...hat.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/x86.c | 65 +++++++++++++++++++++++++++++++++++++++--
2 files changed, 63 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9aa09d330a4b5..77c69aa4756f9 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -599,6 +599,7 @@ struct kvm_arch {
u64 master_kernel_ns;
cycle_t master_cycle_now;
struct delayed_work kvmclock_update_work;
+ bool clocks_synced;
struct kvm_xen_hvm_config xen_hvm_config;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a2d30de597b7d..5cba20b446aac 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1620,6 +1620,60 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
return 0;
}
+static void kvm_schedule_kvmclock_update(struct kvm *kvm, bool now);
+static void clock_sync_fn(struct work_struct *work);
+static DECLARE_DELAYED_WORK(clock_sync_work, clock_sync_fn);
+
+#define CLOCK_SYNC_PERIOD_SECS 300
+#define CLOCK_SYNC_BUMP_SECS 30
+#define CLOCK_SYNC_STEP_MSECS 100
+
+#define __steps(s) (((s) * MSEC_PER_SEC) / CLOCK_SYNC_STEP_MSECS)
+
+static void clock_sync_fn(struct work_struct *work)
+{
+ static unsigned reset_step = __steps(CLOCK_SYNC_PERIOD_SECS);
+ static unsigned step = 0;
+ struct kvm *kvm;
+ bool sync = false;
+
+ spin_lock(&kvm_lock);
+
+ if (step == 0)
+ list_for_each_entry(kvm, &vm_list, vm_list)
+ kvm->arch.clocks_synced = false;
+
+ list_for_each_entry(kvm, &vm_list, vm_list) {
+ if (!kvm->arch.clocks_synced) {
+ kvm_get_kvm(kvm);
+ sync = true;
+ break;
+ }
+ }
+
+ spin_unlock(&kvm_lock);
+
+ if (sync) {
+ kvm_schedule_kvmclock_update(kvm, true);
+ kvm_put_kvm(kvm);
+
+ if (++step == reset_step) {
+ reset_step += __steps(CLOCK_SYNC_BUMP_SECS);
+ pr_warn("kvmclock: reducing VM clock sync frequency "
+ "to every %ld seconds.\n", (reset_step
+ * CLOCK_SYNC_STEP_MSECS)/MSEC_PER_SEC);
+ }
+
+ schedule_delayed_work(&clock_sync_work,
+ msecs_to_jiffies(CLOCK_SYNC_STEP_MSECS));
+ } else {
+ unsigned s = reset_step - step;
+ step = 0;
+ schedule_delayed_work(&clock_sync_work,
+ msecs_to_jiffies(s * CLOCK_SYNC_STEP_MSECS));
+ }
+}
+
/*
* kvmclock updates which are isolated to a given vcpu, such as
* vcpu->cpu migration, should not allow system_timestamp from
@@ -1652,11 +1706,12 @@ static void kvmclock_update_fn(struct work_struct *work)
kvm_put_kvm(kvm);
}
-static void kvm_schedule_kvmclock_update(struct kvm *kvm)
+static void kvm_schedule_kvmclock_update(struct kvm *kvm, bool now)
{
kvm_get_kvm(kvm);
+ kvm->arch.clocks_synced = true;
schedule_delayed_work(&kvm->arch.kvmclock_update_work,
- KVMCLOCK_UPDATE_DELAY);
+ now ? 0 : KVMCLOCK_UPDATE_DELAY);
}
static void kvm_gen_kvmclock_update(struct kvm_vcpu *v)
@@ -1664,7 +1719,7 @@ static void kvm_gen_kvmclock_update(struct kvm_vcpu *v)
struct kvm *kvm = v->kvm;
set_bit(KVM_REQ_CLOCK_UPDATE, &v->requests);
- kvm_schedule_kvmclock_update(kvm);
+ kvm_schedule_kvmclock_update(kvm, false);
}
static bool msr_mtrr_valid(unsigned msr)
@@ -5584,6 +5639,8 @@ int kvm_arch_init(void *opaque)
pvclock_gtod_register_notifier(&pvclock_gtod_notifier);
#endif
+ schedule_delayed_work(&clock_sync_work, CLOCK_SYNC_PERIOD_SECS * HZ);
+
return 0;
out_free_percpu:
@@ -5594,6 +5651,8 @@ out:
void kvm_arch_exit(void)
{
+ cancel_delayed_work_sync(&clock_sync_work);
+
perf_unregister_guest_info_callbacks(&kvm_guest_cbs);
if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
--
1.8.1.4
--
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