On Thu, Aug 28, 2014 at 08:55:18PM +0800, Zhang Haoyu wrote:
> Hi Jason,
> I tested below patch, it's okay, the e1000 interrupt storm disappeared.
> But I am going to make a bit change on it, could you help review it?
>
> >Currently, we call ioapic_service() immediately when we find the irq is still
> >active during eoi broadcast. But for real hardware, there's some dealy
> >between
> >the EOI writing and irq delivery (system bus latency?). So we need to emulate
> >this behavior. Otherwise, for a guest who haven't register a proper irq
> >handler
> >, it would stay in the interrupt routine as this irq would be re-injected
> >immediately after guest enables interrupt. This would lead guest can't move
> >forward and may miss the possibility to get proper irq handler registered
> >(one
> >example is windows guest resuming from hibernation).
> >
> >As there's no way to differ the unhandled irq from new raised ones, this
> >patch
> >solve this problems by scheduling a delayed work when the count of irq
> >injected
> >during eoi broadcast exceeds a threshold value. After this patch, the guest
> >can
> >move a little forward when there's no suitable irq handler in case it may
> >register one very soon and for guest who has a bad irq detection routine (
> >such
> >as note_interrupt() in linux ), this bad irq would be recognized soon as in
> >the
> >past.
> >
> >Signed-off-by: Jason Wang <jasowang <at> redhat.com>
> >---
> > virt/kvm/ioapic.c | 47 +++++++++++++++++++++++++++++++++++++++++++++--
> > virt/kvm/ioapic.h | 2 ++
> > 2 files changed, 47 insertions(+), 2 deletions(-)
> >
> >diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
> >index dcaf272..892253e 100644
> >--- a/virt/kvm/ioapic.c
> >+++ b/virt/kvm/ioapic.c
> > <at> <at> -221,6 +221,24 <at> <at> int kvm_ioapic_set_irq(struct
> > kvm_ioapic *ioapic, int irq, int level)
> > return ret;
> > }
> >
> >+static void kvm_ioapic_eoi_inject_work(struct work_struct *work)
> >+{
> >+ int i, ret;
> >+ struct kvm_ioapic *ioapic = container_of(work, struct kvm_ioapic,
> >+ eoi_inject.work);
> >+ spin_lock(&ioapic->lock);
> >+ for (i = 0; i < IOAPIC_NUM_PINS; i++) {
> >+ union kvm_ioapic_redirect_entry *ent = &ioapic->redirtbl[i];
> >+
> >+ if (ent->fields.trig_mode != IOAPIC_LEVEL_TRIG)
> >+ continue;
> >+
> >+ if (ioapic->irr & (1 << i) && !ent->fields.remote_irr)
> >+ ret = ioapic_service(ioapic, i);
> >+ }
> >+ spin_unlock(&ioapic->lock);
> >+}
> >+
> > static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int vector,
> > int trigger_mode)
> > {
> > <at> <at> -249,8 +267,29 <at> <at> static void
> > __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int vector,
> >
> > ASSERT(ent->fields.trig_mode == IOAPIC_LEVEL_TRIG);
> > ent->fields.remote_irr = 0;
> >- if (!ent->fields.mask && (ioapic->irr & (1 << i)))
> >- ioapic_service(ioapic, i);
> >+ if (!ent->fields.mask && (ioapic->irr & (1 << i))) {
> >+ ++ioapic->irq_eoi;
> -+ ++ioapic->irq_eoi;
> ++ ++ioapic->irq_eoi[i];
> >+ if (ioapic->irq_eoi == 100) {
> -+ if (ioapic->irq_eoi == 100) {
> ++ if (ioapic->irq_eoi[i] == 100) {
> >+ /*
> >+ * Real hardware does not deliver the irq so
> >+ * immediately during eoi broadcast, so we need
> >+ * to emulate this behavior. Otherwise, for
> >+ * guests who has not registered handler of a
> >+ * level irq, this irq would be injected
> >+ * immediately after guest enables interrupt
> >+ * (which happens usually at the end of the
> >+ * common interrupt routine). This would lead
> >+ * guest can't move forward and may miss the
> >+ * possibility to get proper irq handler
> >+ * registered. So we need to give some breath to
> >+ * guest. TODO: 1 is too long?
> >+ */
> >+ schedule_delayed_work(&ioapic->eoi_inject, 1);
> >+ ioapic->irq_eoi = 0;
> -+ ioapic->irq_eoi = 0;
> ++ ioapic->irq_eoi[i] = 0;
> >+ } else {
> >+ ioapic_service(ioapic, i);
> >+ }
> >+ }
> ++ else {
> ++ ioapic->irq_eoi[i] = 0;
> ++ }
> > }
> > }
> I think ioapic->irq_eoi is prone to reach to 100, because during a eoi
> broadcast,
> it's possible that another interrupt's (not current eoi's corresponding
> interrupt) irr is set, so the ioapic->irq_eoi will grow continually,
> and not too long, ioapic->irq_eoi will reach to 100.
> I want to add "u32 irq_eoi[IOAPIC_NUM_PINS];" instead of "u32 irq_eoi;".
> Any ideas?
>
> Zhang Haoyu
I'm a bit concerned how this will affect realtime guests.
Worth adding a flag to enable this, so that e.g. virtio is not
affected?
> >
> > <at> <at> -375,12 +414,14 <at> <at> void kvm_ioapic_reset(struct
> > kvm_ioapic *ioapic)
> > {
> > int i;
> >
> >+ cancel_delayed_work_sync(&ioapic->eoi_inject);
> > for (i = 0; i < IOAPIC_NUM_PINS; i++)
> > ioapic->redirtbl[i].fields.mask = 1;
> > ioapic->base_address = IOAPIC_DEFAULT_BASE_ADDRESS;
> > ioapic->ioregsel = 0;
> > ioapic->irr = 0;
> > ioapic->id = 0;
> >+ ioapic->irq_eoi = 0;
> -+ ioapic->irq_eoi = 0;
> ++ memset(ioapic->irq_eoi, 0x00, IOAPIC_NUM_PINS);
> > update_handled_vectors(ioapic);
> > }
> >
> > <at> <at> -398,6 +439,7 <at> <at> int kvm_ioapic_init(struct kvm *kvm)
> > if (!ioapic)
> > return -ENOMEM;
> > spin_lock_init(&ioapic->lock);
> >+ INIT_DELAYED_WORK(&ioapic->eoi_inject, kvm_ioapic_eoi_inject_work);
> > kvm->arch.vioapic = ioapic;
> > kvm_ioapic_reset(ioapic);
> > kvm_iodevice_init(&ioapic->dev, &ioapic_mmio_ops);
> > <at> <at> -418,6 +460,7 <at> <at> void kvm_ioapic_destroy(struct kvm
> > *kvm)
> > {
> > struct kvm_ioapic *ioapic = kvm->arch.vioapic;
> >
> >+ cancel_delayed_work_sync(&ioapic->eoi_inject);
> > if (ioapic) {
> > kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &ioapic->dev);
> > kvm->arch.vioapic = NULL;
> >diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h
> >index 0b190c3..8938e66 100644
> >--- a/virt/kvm/ioapic.h
> >+++ b/virt/kvm/ioapic.h
> > <at> <at> -47,6 +47,8 <at> <at> struct kvm_ioapic {
> > void (*ack_notifier)(void *opaque, int irq);
> > spinlock_t lock;
> > DECLARE_BITMAP(handled_vectors, 256);
> >+ struct delayed_work eoi_inject;
> >+ u32 irq_eoi;
> -+ u32 irq_eoi;
> ++ u32 irq_eoi[IOAPIC_NUM_PINS];
> > };
> >
> > #ifdef DEBUG
>
