KVM: Allow host IRQ sharing for assigned PCI 2.3 devices
PCI 2.3 allows to generically disable IRQ sources at device level. This
enables us to share legacy IRQs of such devices with other host devices
when passing them to a guest.
The new IRQ sharing feature introduced here is optional, user space has
to request it explicitly. Moreover, user space can inform us about its
view of PCI_COMMAND_INTX_DISABLE so that we can avoid unmasking the
interrupt and signaling it if the guest masked it via the virtualized
PCI config space.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index ece8061..08e0571 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -55,23 +55,67 @@
return index;
}
-static irqreturn_t kvm_assigned_dev_thread(int irq, void *dev_id)
+static irqreturn_t kvm_assigned_dev_intx(int irq, void *dev_id)
+{
+ struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
+ int ret;
+
+ spin_lock(&assigned_dev->intx_lock);
+ if (pci_check_and_mask_intx(assigned_dev->dev)) {
+ assigned_dev->host_irq_disabled = true;
+ ret = IRQ_WAKE_THREAD;
+ } else
+ ret = IRQ_NONE;
+ spin_unlock(&assigned_dev->intx_lock);
+
+ return ret;
+}
+
+static void
+kvm_assigned_dev_raise_guest_irq(struct kvm_assigned_dev_kernel *assigned_dev,
+ int vector)
+{
+ if (unlikely(assigned_dev->irq_requested_type &
+ KVM_DEV_IRQ_GUEST_INTX)) {
+ mutex_lock(&assigned_dev->intx_mask_lock);
+ if (!(assigned_dev->flags & KVM_DEV_ASSIGN_MASK_INTX))
+ kvm_set_irq(assigned_dev->kvm,
+ assigned_dev->irq_source_id, vector, 1);
+ mutex_unlock(&assigned_dev->intx_mask_lock);
+ } else
+ kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id,
+ vector, 1);
+}
+
+static irqreturn_t kvm_assigned_dev_thread_intx(int irq, void *dev_id)
{
struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
- if (assigned_dev->irq_requested_type & KVM_DEV_IRQ_HOST_INTX) {
- spin_lock(&assigned_dev->intx_lock);
+ if (!(assigned_dev->flags & KVM_DEV_ASSIGN_PCI_2_3)) {
+ spin_lock_irq(&assigned_dev->intx_lock);
disable_irq_nosync(irq);
assigned_dev->host_irq_disabled = true;
- spin_unlock(&assigned_dev->intx_lock);
+ spin_unlock_irq(&assigned_dev->intx_lock);
}
- kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id,
- assigned_dev->guest_irq, 1);
+ kvm_assigned_dev_raise_guest_irq(assigned_dev,
+ assigned_dev->guest_irq);
return IRQ_HANDLED;
}
+#ifdef __KVM_HAVE_MSI
+static irqreturn_t kvm_assigned_dev_thread_msi(int irq, void *dev_id)
+{
+ struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
+
+ kvm_assigned_dev_raise_guest_irq(assigned_dev,
+ assigned_dev->guest_irq);
+
+ return IRQ_HANDLED;
+}
+#endif
+
#ifdef __KVM_HAVE_MSIX
static irqreturn_t kvm_assigned_dev_thread_msix(int irq, void *dev_id)
{
@@ -81,8 +125,7 @@
if (index >= 0) {
vector = assigned_dev->guest_msix_entries[index].vector;
- kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id,
- vector, 1);
+ kvm_assigned_dev_raise_guest_irq(assigned_dev, vector);
}
return IRQ_HANDLED;
@@ -98,15 +141,31 @@
kvm_set_irq(dev->kvm, dev->irq_source_id, dev->guest_irq, 0);
- /* The guest irq may be shared so this ack may be
- * from another device.
- */
- spin_lock(&dev->intx_lock);
- if (dev->host_irq_disabled) {
- enable_irq(dev->host_irq);
- dev->host_irq_disabled = false;
+ mutex_lock(&dev->intx_mask_lock);
+
+ if (!(dev->flags & KVM_DEV_ASSIGN_MASK_INTX)) {
+ bool reassert = false;
+
+ spin_lock_irq(&dev->intx_lock);
+ /*
+ * The guest IRQ may be shared so this ack can come from an
+ * IRQ for another guest device.
+ */
+ if (dev->host_irq_disabled) {
+ if (!(dev->flags & KVM_DEV_ASSIGN_PCI_2_3))
+ enable_irq(dev->host_irq);
+ else if (!pci_check_and_unmask_intx(dev->dev))
+ reassert = true;
+ dev->host_irq_disabled = reassert;
+ }
+ spin_unlock_irq(&dev->intx_lock);
+
+ if (reassert)
+ kvm_set_irq(dev->kvm, dev->irq_source_id,
+ dev->guest_irq, 1);
}
- spin_unlock(&dev->intx_lock);
+
+ mutex_unlock(&dev->intx_mask_lock);
}
static void deassign_guest_irq(struct kvm *kvm,
@@ -154,7 +213,15 @@
pci_disable_msix(assigned_dev->dev);
} else {
/* Deal with MSI and INTx */
- disable_irq(assigned_dev->host_irq);
+ if ((assigned_dev->irq_requested_type &
+ KVM_DEV_IRQ_HOST_INTX) &&
+ (assigned_dev->flags & KVM_DEV_ASSIGN_PCI_2_3)) {
+ spin_lock_irq(&assigned_dev->intx_lock);
+ pci_intx(assigned_dev->dev, false);
+ spin_unlock_irq(&assigned_dev->intx_lock);
+ synchronize_irq(assigned_dev->host_irq);
+ } else
+ disable_irq(assigned_dev->host_irq);
free_irq(assigned_dev->host_irq, assigned_dev);
@@ -235,15 +302,34 @@
static int assigned_device_enable_host_intx(struct kvm *kvm,
struct kvm_assigned_dev_kernel *dev)
{
+ irq_handler_t irq_handler;
+ unsigned long flags;
+
dev->host_irq = dev->dev->irq;
- /* Even though this is PCI, we don't want to use shared
- * interrupts. Sharing host devices with guest-assigned devices
- * on the same interrupt line is not a happy situation: there
- * are going to be long delays in accepting, acking, etc.
+
+ /*
+ * We can only share the IRQ line with other host devices if we are
+ * able to disable the IRQ source at device-level - independently of
+ * the guest driver. Otherwise host devices may suffer from unbounded
+ * IRQ latencies when the guest keeps the line asserted.
*/
- if (request_threaded_irq(dev->host_irq, NULL, kvm_assigned_dev_thread,
- IRQF_ONESHOT, dev->irq_name, dev))
+ if (dev->flags & KVM_DEV_ASSIGN_PCI_2_3) {
+ irq_handler = kvm_assigned_dev_intx;
+ flags = IRQF_SHARED;
+ } else {
+ irq_handler = NULL;
+ flags = IRQF_ONESHOT;
+ }
+ if (request_threaded_irq(dev->host_irq, irq_handler,
+ kvm_assigned_dev_thread_intx, flags,
+ dev->irq_name, dev))
return -EIO;
+
+ if (dev->flags & KVM_DEV_ASSIGN_PCI_2_3) {
+ spin_lock_irq(&dev->intx_lock);
+ pci_intx(dev->dev, true);
+ spin_unlock_irq(&dev->intx_lock);
+ }
return 0;
}
@@ -260,8 +346,9 @@
}
dev->host_irq = dev->dev->irq;
- if (request_threaded_irq(dev->host_irq, NULL, kvm_assigned_dev_thread,
- 0, dev->irq_name, dev)) {
+ if (request_threaded_irq(dev->host_irq, NULL,
+ kvm_assigned_dev_thread_msi, 0,
+ dev->irq_name, dev)) {
pci_disable_msi(dev->dev);
return -EIO;
}
@@ -319,7 +406,6 @@
{
dev->guest_irq = irq->guest_irq;
dev->ack_notifier.gsi = -1;
- dev->host_irq_disabled = false;
return 0;
}
#endif
@@ -331,7 +417,6 @@
{
dev->guest_irq = irq->guest_irq;
dev->ack_notifier.gsi = -1;
- dev->host_irq_disabled = false;
return 0;
}
#endif
@@ -365,6 +450,7 @@
default:
r = -EINVAL;
}
+ dev->host_irq_disabled = false;
if (!r)
dev->irq_requested_type |= host_irq_type;
@@ -466,6 +552,7 @@
{
int r = -ENODEV;
struct kvm_assigned_dev_kernel *match;
+ unsigned long irq_type;
mutex_lock(&kvm->lock);
@@ -474,7 +561,9 @@
if (!match)
goto out;
- r = kvm_deassign_irq(kvm, match, assigned_irq->flags);
+ irq_type = assigned_irq->flags & (KVM_DEV_IRQ_HOST_MASK |
+ KVM_DEV_IRQ_GUEST_MASK);
+ r = kvm_deassign_irq(kvm, match, irq_type);
out:
mutex_unlock(&kvm->lock);
return r;
@@ -607,6 +696,10 @@
if (!match->pci_saved_state)
printk(KERN_DEBUG "%s: Couldn't store %s saved state\n",
__func__, dev_name(&dev->dev));
+
+ if (!pci_intx_mask_supported(dev))
+ assigned_dev->flags &= ~KVM_DEV_ASSIGN_PCI_2_3;
+
match->assigned_dev_id = assigned_dev->assigned_dev_id;
match->host_segnr = assigned_dev->segnr;
match->host_busnr = assigned_dev->busnr;
@@ -614,6 +707,7 @@
match->flags = assigned_dev->flags;
match->dev = dev;
spin_lock_init(&match->intx_lock);
+ mutex_init(&match->intx_mask_lock);
match->irq_source_id = -1;
match->kvm = kvm;
match->ack_notifier.irq_acked = kvm_assigned_dev_ack_irq;
@@ -759,6 +853,55 @@
}
#endif
+static int kvm_vm_ioctl_set_pci_irq_mask(struct kvm *kvm,
+ struct kvm_assigned_pci_dev *assigned_dev)
+{
+ int r = 0;
+ struct kvm_assigned_dev_kernel *match;
+
+ mutex_lock(&kvm->lock);
+
+ match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
+ assigned_dev->assigned_dev_id);
+ if (!match) {
+ r = -ENODEV;
+ goto out;
+ }
+
+ mutex_lock(&match->intx_mask_lock);
+
+ match->flags &= ~KVM_DEV_ASSIGN_MASK_INTX;
+ match->flags |= assigned_dev->flags & KVM_DEV_ASSIGN_MASK_INTX;
+
+ if (match->irq_requested_type & KVM_DEV_IRQ_GUEST_INTX) {
+ if (assigned_dev->flags & KVM_DEV_ASSIGN_MASK_INTX) {
+ kvm_set_irq(match->kvm, match->irq_source_id,
+ match->guest_irq, 0);
+ /*
+ * Masking at hardware-level is performed on demand,
+ * i.e. when an IRQ actually arrives at the host.
+ */
+ } else if (!(assigned_dev->flags & KVM_DEV_ASSIGN_PCI_2_3)) {
+ /*
+ * Unmask the IRQ line if required. Unmasking at
+ * device level will be performed by user space.
+ */
+ spin_lock_irq(&match->intx_lock);
+ if (match->host_irq_disabled) {
+ enable_irq(match->host_irq);
+ match->host_irq_disabled = false;
+ }
+ spin_unlock_irq(&match->intx_lock);
+ }
+ }
+
+ mutex_unlock(&match->intx_mask_lock);
+
+out:
+ mutex_unlock(&kvm->lock);
+ return r;
+}
+
long kvm_vm_ioctl_assigned_device(struct kvm *kvm, unsigned ioctl,
unsigned long arg)
{
@@ -866,6 +1009,15 @@
break;
}
#endif
+ case KVM_ASSIGN_SET_INTX_MASK: {
+ struct kvm_assigned_pci_dev assigned_dev;
+
+ r = -EFAULT;
+ if (copy_from_user(&assigned_dev, argp, sizeof assigned_dev))
+ goto out;
+ r = kvm_vm_ioctl_set_pci_irq_mask(kvm, &assigned_dev);
+ break;
+ }
default:
r = -ENOTTY;
break;
@@ -873,4 +1025,3 @@
out:
return r;
}
-