virtio-mem-pci: Allow setting nvectors, so we can use MSI-X

Let's do it similar as virtio-balloon-pci. With this change, we can
use virtio-mem-pci on s390x, although plugging will still fail until
properly wired up in the machine.

No need to worry about transitional/non_transitional devices, because they
don't exist for virtio-mem.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20250128185705.1609038-2-david@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/core/machine.c

@@ -41,6 +41,7 @@ GlobalProperty hw_compat_9_2[] = {
     { "virtio-balloon-pci", "vectors", "0" },
     { "virtio-balloon-pci-transitional", "vectors", "0" },
     { "virtio-balloon-pci-non-transitional", "vectors", "0" },
+    { "virtio-mem-pci", "vectors", "0" },
 };
 const size_t hw_compat_9_2_len = G_N_ELEMENTS(hw_compat_9_2);
 

hw/virtio/virtio-mem-pci.c

@@ -22,6 +22,10 @@ static void virtio_mem_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
     VirtIOMEMPCI *mem_pci = VIRTIO_MEM_PCI(vpci_dev);
     DeviceState *vdev = DEVICE(&mem_pci->vdev);
 
+    if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
+        vpci_dev->nvectors = 2;
+    }
+
     virtio_pci_force_virtio_1(vpci_dev);
     qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
 }
@@ -152,6 +156,13 @@ static void virtio_mem_pci_set_requested_size(Object *obj, Visitor *v,
     object_property_set(OBJECT(&pci_mem->vdev), name, v, errp);
 }
 
+static const Property virtio_mem_pci_class_properties[] = {
+    DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
+                    VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
+    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors,
+                       DEV_NVECTORS_UNSPECIFIED),
+};
+
 static void virtio_mem_pci_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
@@ -164,6 +175,7 @@ static void virtio_mem_pci_class_init(ObjectClass *klass, void *data)
     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
     pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
     pcidev_k->class_id = PCI_CLASS_OTHERS;
+    device_class_set_props(dc, virtio_mem_pci_class_properties);
 
     mdc->get_addr = virtio_mem_pci_get_addr;
     mdc->set_addr = virtio_mem_pci_set_addr;