If we need to inject an MSI into the guest, we rely at the moment on a
working GSI MSI routing functionality. However we can get away without
IRQ routing, if the host supports MSI injection via the KVM_SIGNAL_MSI
ioctl.
So we try the GSI routing first, but if that fails due to a missing
IRQ routing functionality, we fall back to KVM_SIGNAL_MSI (if that is
supported).
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
virtio/pci.c | 29 ++++++++++++++++++++++++++---
1 file changed, 26 insertions(+), 3 deletions(-)
diff --git a/virtio/pci.c b/virtio/pci.c
index e9f36c7..04176c1 100644
--- a/virtio/pci.c
+++ b/virtio/pci.c
@@ -193,8 +193,20 @@ static bool virtio_pci__specific_io_out(struct kvm *kvm, struct virtio_device *v
gsi = irq__add_msix_route(kvm,
&vpci->msix_table[vec].msg);
- if (gsi >= 0)
- vpci->config_gsi = gsi;
+ /*
+ * We don't need IRQ routing if we can use
+ * MSI injection via the KVM_SIGNAL_MSI ioctl.
+ */
+ if (gsi == -ENXIO &&
+ vpci->features & VIRTIO_PCI_F_SIGNAL_MSI)
+ break;
+
+ if (gsi < 0) {
+ die("failed to configure MSIs");
+ break;
+ }
+
+ vpci->config_gsi = gsi;
break;
case VIRTIO_MSI_QUEUE_VECTOR:
vec = ioport__read16(data);
@@ -205,8 +217,19 @@ static bool virtio_pci__specific_io_out(struct kvm *kvm, struct virtio_device *v
gsi = irq__add_msix_route(kvm,
&vpci->msix_table[vec].msg);
- if (gsi < 0)
+ /*
+ * We don't need IRQ routing if we can use
+ * MSI injection via the KVM_SIGNAL_MSI ioctl.
+ */
+ if (gsi == -ENXIO &&
+ vpci->features & VIRTIO_PCI_F_SIGNAL_MSI)
break;
+
+ if (gsi < 0) {
+ die("failed to configure MSIs");
+ break;
+ }
+
vpci->gsis[vpci->queue_selector] = gsi;
if (vdev->ops->notify_vq_gsi)
vdev->ops->notify_vq_gsi(kvm, vpci->dev,
--
2.9.0
