This gives management tools like libvirt a chance to open the vfio
cdev with privilege and pass FD to qemu. This way qemu never needs
to have privilege to open a VFIO or iommu cdev node.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 hw/vfio/platform.c | 41 +++++++++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 8 deletions(-)

diff --git a/hw/vfio/platform.c b/hw/vfio/platform.c
index 86e176ee97..59a50b1598 100644
--- a/hw/vfio/platform.c
+++ b/hw/vfio/platform.c
@@ -36,6 +36,7 @@
 #include "hw/platform-bus.h"
 #include "hw/qdev-properties.h"
 #include "sysemu/kvm.h"
+#include "monitor/monitor.h"
 
 /*
  * Functions used whatever the injection method
@@ -530,14 +531,13 @@ static VFIODeviceOps vfio_platform_ops = {
  */
 static int vfio_base_device_init(VFIODevice *vbasedev, Error **errp)
 {
-    struct stat st;
     int ret;
 
-    /* @sysfsdev takes precedence over @host */
-    if (vbasedev->sysfsdev) {
+    /* @fd takes precedence over @sysfsdev which takes precedence over @host */
+    if (vbasedev->fd < 0 && vbasedev->sysfsdev) {
         g_free(vbasedev->name);
         vbasedev->name = g_path_get_basename(vbasedev->sysfsdev);
-    } else {
+    } else if (vbasedev->fd < 0) {
         if (!vbasedev->name || strchr(vbasedev->name, '/')) {
             error_setg(errp, "wrong host device name");
             return -EINVAL;
@@ -547,10 +547,9 @@ static int vfio_base_device_init(VFIODevice *vbasedev, Error **errp)
                                              vbasedev->name);
     }
 
-    if (stat(vbasedev->sysfsdev, &st) < 0) {
-        error_setg_errno(errp, errno,
-                         "failed to get the sysfs host device file status");
-        return -errno;
+    ret = vfio_device_get_name(vbasedev, errp);
+    if (ret) {
+        return ret;
     }
 
     ret = vfio_attach_device(vbasedev->name, vbasedev,
@@ -657,6 +656,28 @@ static Property vfio_platform_dev_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static void vfio_platform_instance_init(Object *obj)
+{
+    VFIOPlatformDevice *vdev = VFIO_PLATFORM_DEVICE(obj);
+
+    vdev->vbasedev.fd = -1;
+}
+
+#ifdef CONFIG_IOMMUFD
+static void vfio_platform_set_fd(Object *obj, const char *str, Error **errp)
+{
+    VFIOPlatformDevice *vdev = VFIO_PLATFORM_DEVICE(obj);
+    int fd = -1;
+
+    fd = monitor_fd_param(monitor_cur(), str, errp);
+    if (fd == -1) {
+        error_prepend(errp, "Could not parse remote object fd %s:", str);
+        return;
+    }
+    vdev->vbasedev.fd = fd;
+}
+#endif
+
 static void vfio_platform_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
@@ -664,6 +685,9 @@ static void vfio_platform_class_init(ObjectClass *klass, void *data)
 
     dc->realize = vfio_platform_realize;
     device_class_set_props(dc, vfio_platform_dev_properties);
+#ifdef CONFIG_IOMMUFD
+    object_class_property_add_str(klass, "fd", NULL, vfio_platform_set_fd);
+#endif
     dc->vmsd = &vfio_platform_vmstate;
     dc->desc = "VFIO-based platform device assignment";
     sbc->connect_irq_notifier = vfio_start_irqfd_injection;
@@ -676,6 +700,7 @@ static const TypeInfo vfio_platform_dev_info = {
     .name = TYPE_VFIO_PLATFORM,
     .parent = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(VFIOPlatformDevice),
+    .instance_init = vfio_platform_instance_init,
     .class_init = vfio_platform_class_init,
     .class_size = sizeof(VFIOPlatformDeviceClass),
 };
-- 
2.34.1