KVM: fix handling of ACK from shared guest IRQ
If an assigned device shares a guest irq with an emulated
device then we currently interpret an ack generated by the
emulated device as originating from the assigned device
leading to e.g. "Unbalanced enable for IRQ 4347" from the
enable_irq() in kvm_assigned_dev_ack_irq().
The fix is fairly simple - don't enable the physical device
irq unless it was previously disabled.
Of course, this can still lead to a situation where a
non-assigned device ACK can cause the physical device irq to
be reenabled before the device was serviced. However, being
level sensitive, the interrupt will merely be regenerated.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index eb70ca6..fc6127c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -170,6 +170,7 @@
KVM_ASSIGNED_DEV_GUEST_MSI) {
assigned_device_msi_dispatch(assigned_dev);
enable_irq(assigned_dev->host_irq);
+ assigned_dev->host_irq_disabled = false;
}
mutex_unlock(&assigned_dev->kvm->lock);
kvm_put_kvm(assigned_dev->kvm);
@@ -181,8 +182,12 @@
(struct kvm_assigned_dev_kernel *) dev_id;
kvm_get_kvm(assigned_dev->kvm);
+
schedule_work(&assigned_dev->interrupt_work);
+
disable_irq_nosync(irq);
+ assigned_dev->host_irq_disabled = true;
+
return IRQ_HANDLED;
}
@@ -196,8 +201,16 @@
dev = container_of(kian, struct kvm_assigned_dev_kernel,
ack_notifier);
+
kvm_set_irq(dev->kvm, dev->irq_source_id, dev->guest_irq, 0);
- enable_irq(dev->host_irq);
+
+ /* The guest irq may be shared so this ack may be
+ * from another device.
+ */
+ if (dev->host_irq_disabled) {
+ enable_irq(dev->host_irq);
+ dev->host_irq_disabled = false;
+ }
}
static void kvm_free_assigned_irq(struct kvm *kvm,