vfio/{iommufd, container}: Invoke HostIOMMUDevice::realize() during attach_device()

Move the HostIOMMUDevice::realize() to be invoked during the attach of the device
before we allocate IOMMUFD hardware pagetable objects (HWPT). This allows the use
of the hw_caps obtained by IOMMU_GET_HW_INFO that essentially tell if the IOMMU
behind the device supports dirty tracking.

Note: The HostIOMMUDevice data from legacy backend is static and doesn't
need any information from the (type1-iommu) backend to be initialized.
In contrast however, the IOMMUFD HostIOMMUDevice data requires the
iommufd FD to be connected and having a devid to be able to successfully
GET_HW_INFO. This means vfio_device_hiod_realize() is called in
different places within the backend .attach_device() implementation.

Suggested-by: Cédric Le Goater <clg@redhat.cm>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
[ clg: Fixed error handling in iommufd_cdev_attach() ]
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

hw/vfio/common.c

@@ -1536,7 +1536,7 @@ bool vfio_attach_device(char *name, VFIODevice *vbasedev,
 {
     const VFIOIOMMUClass *ops =
         VFIO_IOMMU_CLASS(object_class_by_name(TYPE_VFIO_IOMMU_LEGACY));
-    HostIOMMUDevice *hiod;
+    HostIOMMUDevice *hiod = NULL;
 
     if (vbasedev->iommufd) {
         ops = VFIO_IOMMU_CLASS(object_class_by_name(TYPE_VFIO_IOMMU_IOMMUFD));
@@ -1544,21 +1544,17 @@ bool vfio_attach_device(char *name, VFIODevice *vbasedev,
 
     assert(ops);
 
-    if (!ops->attach_device(name, vbasedev, as, errp)) {
-        return false;
-    }
-
-    if (vbasedev->mdev) {
-        return true;
-    }
 
+    if (!vbasedev->mdev) {
         hiod = HOST_IOMMU_DEVICE(object_new(ops->hiod_typename));
-    if (!HOST_IOMMU_DEVICE_GET_CLASS(hiod)->realize(hiod, vbasedev, errp)) {
+        vbasedev->hiod = hiod;
+    }
+
+    if (!ops->attach_device(name, vbasedev, as, errp)) {
         object_unref(hiod);
-        ops->detach_device(vbasedev);
+        vbasedev->hiod = NULL;
         return false;
     }
-    vbasedev->hiod = hiod;
 
     return true;
 }

hw/vfio/container.c

@@ -914,6 +914,10 @@ static bool vfio_legacy_attach_device(const char *name, VFIODevice *vbasedev,
 
     trace_vfio_attach_device(vbasedev->name, groupid);
 
+    if (!vfio_device_hiod_realize(vbasedev, errp)) {
+        return false;
+    }
+
     group = vfio_get_group(groupid, as, errp);
     if (!group) {
         return false;

hw/vfio/helpers.c

@@ -689,3 +689,14 @@ bool vfio_device_is_mdev(VFIODevice *vbasedev)
     subsys = realpath(tmp, NULL);
     return subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);
 }
+
+bool vfio_device_hiod_realize(VFIODevice *vbasedev, Error **errp)
+{
+    HostIOMMUDevice *hiod = vbasedev->hiod;
+
+    if (!hiod) {
+        return true;
+    }
+
+    return HOST_IOMMU_DEVICE_GET_CLASS(hiod)->realize(hiod, vbasedev, errp);
+}

hw/vfio/iommufd.c

@@ -404,6 +404,17 @@ static bool iommufd_cdev_attach(const char *name, VFIODevice *vbasedev,
 
     space = vfio_get_address_space(as);
 
+    /*
+     * The HostIOMMUDevice data from legacy backend is static and doesn't need
+     * any information from the (type1-iommu) backend to be initialized. In
+     * contrast however, the IOMMUFD HostIOMMUDevice data requires the iommufd
+     * FD to be connected and having a devid to be able to successfully call
+     * iommufd_backend_get_device_info().
+     */
+    if (!vfio_device_hiod_realize(vbasedev, errp)) {
+        goto err_alloc_ioas;
+    }
+
     /* try to attach to an existing container in this space */
     QLIST_FOREACH(bcontainer, &space->containers, next) {
         container = container_of(bcontainer, VFIOIOMMUFDContainer, bcontainer);

include/hw/vfio/vfio-common.h

@@ -242,6 +242,7 @@ void vfio_region_finalize(VFIORegion *region);
 void vfio_reset_handler(void *opaque);
 struct vfio_device_info *vfio_get_device_info(int fd);
 bool vfio_device_is_mdev(VFIODevice *vbasedev);
+bool vfio_device_hiod_realize(VFIODevice *vbasedev, Error **errp);
 bool vfio_attach_device(char *name, VFIODevice *vbasedev,
                         AddressSpace *as, Error **errp);
 void vfio_detach_device(VFIODevice *vbasedev);