vfio-user: implement message send infrastructure

Add plumbing for sending vfio-user messages on the control socket.
Add initial version negotation on connection.

Originally-by: John Johnson <john.g.johnson@oracle.com>
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250625193012.2316242-5-john.levon@nutanix.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

1 files changed, 18 insertions, 2 deletions

diff --git a/hw/vfio-user/pci.c b/hw/vfio-user/pci.c
index bad2829f5c..61f525cf4a 100644
--- a/hw/vfio-user/pci.c
+++ b/hw/vfio-user/pci.c
@@ -20,6 +20,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(VFIOUserPCIDevice, VFIO_USER_PCI)
 struct VFIOUserPCIDevice {
     VFIOPCIDevice device;
     SocketAddress *socket;
+    bool send_queued;   /* all sends are queued */
 };
 
 /*
@@ -92,6 +93,16 @@ static void vfio_user_pci_realize(PCIDevice *pdev, Error **errp)
     vbasedev->proxy = proxy;
     vfio_user_set_handler(vbasedev, vfio_user_pci_process_req, vdev);
 
+    vbasedev->name = g_strdup_printf("vfio-user:%s", sock_name);
+
+    if (udev->send_queued) {
+        proxy->flags |= VFIO_PROXY_FORCE_QUEUED;
+    }
+
+    if (!vfio_user_validate_version(proxy, errp)) {
+        goto error;
+    }
+
     /*
      * vfio-user devices are effectively mdevs (don't use a host iommu).
      */
@@ -101,9 +112,13 @@ static void vfio_user_pci_realize(PCIDevice *pdev, Error **errp)
     if (!vfio_device_attach_by_iommu_type(TYPE_VFIO_IOMMU_USER,
                                           vbasedev->name, vbasedev,
                                           as, errp)) {
-        error_prepend(errp, VFIO_MSG_PREFIX, vbasedev->name);
-        return;
+        goto error;
     }
+
+    return;
+
+error:
+    error_prepend(errp, VFIO_MSG_PREFIX, vdev->vbasedev.name);
 }
 
 static void vfio_user_instance_init(Object *obj)
@@ -153,6 +168,7 @@ static const Property vfio_user_pci_dev_properties[] = {
                        sub_vendor_id, PCI_ANY_ID),
     DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice,
                        sub_device_id, PCI_ANY_ID),
+    DEFINE_PROP_BOOL("x-send-queued", VFIOUserPCIDevice, send_queued, false),
 };
 
 static void vfio_user_pci_set_socket(Object *obj, Visitor *v, const char *name,