vfio/iommufd: preserve descriptors

Save the iommu and vfio device fd in CPR state when it is created.
After CPR, the fd number is found in CPR state and reused.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Link: https://lore.kernel.org/qemu-devel/1751493538-202042-16-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

2 files changed, 11 insertions, 8 deletions

diff --git a/hw/vfio/cpr-iommufd.c b/hw/vfio/cpr-iommufd.c
index 4166201..a72b68d 100644
--- a/hw/vfio/cpr-iommufd.c
+++ b/hw/vfio/cpr-iommufd.c
@@ -166,12 +166,18 @@ void vfio_iommufd_cpr_unregister_container(VFIOIOMMUFDContainer *container)
 void vfio_iommufd_cpr_register_device(VFIODevice *vbasedev)
 {
     if (!cpr_is_incoming()) {
+        /*
+         * Beware fd may have already been saved by vfio_device_set_fd,
+         * so call resave to avoid a duplicate entry.
+         */
+        cpr_resave_fd(vbasedev->name, 0, vbasedev->fd);
         vfio_cpr_save_device(vbasedev);
     }
 }
 
 void vfio_iommufd_cpr_unregister_device(VFIODevice *vbasedev)
 {
+    cpr_delete_fd(vbasedev->name, 0);
     vfio_cpr_delete_device(vbasedev->name);
 }
 
@@ -180,5 +186,9 @@ void vfio_cpr_load_device(VFIODevice *vbasedev)
     if (cpr_is_incoming()) {
         bool ret = vfio_cpr_find_device(vbasedev);
         g_assert(ret);
+
+        if (vbasedev->fd < 0) {
+            vbasedev->fd = cpr_find_fd(vbasedev->name, 0);
+        }
     }
 }
diff --git a/hw/vfio/device.c b/hw/vfio/device.c
index 0ae3f3c..96cf214 100644
--- a/hw/vfio/device.c
+++ b/hw/vfio/device.c
@@ -351,14 +351,7 @@ void vfio_device_free_name(VFIODevice *vbasedev)
 
 void vfio_device_set_fd(VFIODevice *vbasedev, const char *str, Error **errp)
 {
-    ERRP_GUARD();
-    int fd = monitor_fd_param(monitor_cur(), str, errp);
-
-    if (fd < 0) {
-        error_prepend(errp, "Could not parse remote object fd %s:", str);
-        return;
-    }
-    vbasedev->fd = fd;
+    vbasedev->fd = cpr_get_fd_param(vbasedev->dev->id, str, 0, errp);
 }
 
 static VFIODeviceIOOps vfio_device_io_ops_ioctl;