On Wed, Feb 26, 2014 at 07:15:12PM +0100, Andrew Jones wrote: > 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 <drjo...@redhat.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);
Better have it per vm to avoid 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); > + } Can you explain the variable sync frequency? To be based on NTP frequency correction? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html