kvm: ioapic: conditionally delay irq delivery duringeoi broadcast
Currently, we call ioapic_service() immediately when we find the irq is still
active during eoi broadcast. But for real hardware, there's some delay between
the EOI writing and irq delivery. If we do not emulate this behavior, and
re-inject the interrupt immediately after the guest sends an EOI and re-enables
interrupts, a guest might spend all its time in the ISR if it has a broken
handler for a level-triggered interrupt.
Such livelock actually happens with Windows guests when resuming from
hibernation.
As there's no way to recognize the broken handle from new raised ones, this patch
delays an interrupt if 10.000 consecutive EOIs found that the interrupt was
still high. The guest can then make a little forward progress, until a proper
IRQ handler is set or until some detection routine in the guest (such as
Linux's note_interrupt()) recognizes the situation.
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Zhang Haoyu <zhanghy@sangfor.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index 908925a..ab679c3 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -95,6 +95,26 @@
__entry->coalesced ? " (coalesced)" : "")
);
+TRACE_EVENT(kvm_ioapic_delayed_eoi_inj,
+ TP_PROTO(__u64 e),
+ TP_ARGS(e),
+
+ TP_STRUCT__entry(
+ __field( __u64, e )
+ ),
+
+ TP_fast_assign(
+ __entry->e = e;
+ ),
+
+ TP_printk("dst %x vec=%u (%s|%s|%s%s)",
+ (u8)(__entry->e >> 56), (u8)__entry->e,
+ __print_symbolic((__entry->e >> 8 & 0x7), kvm_deliver_mode),
+ (__entry->e & (1<<11)) ? "logical" : "physical",
+ (__entry->e & (1<<15)) ? "level" : "edge",
+ (__entry->e & (1<<16)) ? "|masked" : "")
+);
+
TRACE_EVENT(kvm_msi_set_irq,
TP_PROTO(__u64 address, __u64 data),
TP_ARGS(address, data),
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index e8ce34c..0ba4057 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -405,6 +405,26 @@
spin_unlock(&ioapic->lock);
}
+static void kvm_ioapic_eoi_inject_work(struct work_struct *work)
+{
+ int i;
+ 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)
+ ioapic_service(ioapic, i, false);
+ }
+ spin_unlock(&ioapic->lock);
+}
+
+#define IOAPIC_SUCCESSIVE_IRQ_MAX_COUNT 10000
+
static void __kvm_ioapic_update_eoi(struct kvm_vcpu *vcpu,
struct kvm_ioapic *ioapic, int vector, int trigger_mode)
{
@@ -435,8 +455,26 @@
ASSERT(ent->fields.trig_mode == IOAPIC_LEVEL_TRIG);
ent->fields.remote_irr = 0;
- if (ioapic->irr & (1 << i))
- ioapic_service(ioapic, i, false);
+ if (!ent->fields.mask && (ioapic->irr & (1 << i))) {
+ ++ioapic->irq_eoi[i];
+ if (ioapic->irq_eoi[i] == IOAPIC_SUCCESSIVE_IRQ_MAX_COUNT) {
+ /*
+ * Real hardware does not deliver the interrupt
+ * immediately during eoi broadcast, and this
+ * lets a buggy guest make slow progress
+ * even if it does not correctly handle a
+ * level-triggered interrupt. Emulate this
+ * behavior if we detect an interrupt storm.
+ */
+ schedule_delayed_work(&ioapic->eoi_inject, HZ / 100);
+ ioapic->irq_eoi[i] = 0;
+ trace_kvm_ioapic_delayed_eoi_inj(ent->bits);
+ } else {
+ ioapic_service(ioapic, i, false);
+ }
+ } else {
+ ioapic->irq_eoi[i] = 0;
+ }
}
}
@@ -565,12 +603,14 @@
{
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;
+ memset(ioapic->irq_eoi, 0x00, IOAPIC_NUM_PINS);
rtc_irq_eoi_tracking_reset(ioapic);
update_handled_vectors(ioapic);
}
@@ -589,6 +629,7 @@
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);
@@ -609,6 +650,7 @@
{
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 90d43e9..e23b706 100644
--- a/virt/kvm/ioapic.h
+++ b/virt/kvm/ioapic.h
@@ -59,6 +59,8 @@
spinlock_t lock;
DECLARE_BITMAP(handled_vectors, 256);
struct rtc_status rtc_status;
+ struct delayed_work eoi_inject;
+ u32 irq_eoi[IOAPIC_NUM_PINS];
};
#ifdef DEBUG
