vhost: Distinguish errors in vhost_dev_get_config()

Instead of just returning 0/-1 and letting the caller make up a
meaningless error message, add an Error parameter to allow reporting the
real error and switch to 0/-errno so that different kind of errors can
be distinguished in the caller.

config_len in vhost_user_get_config() is defined by the device, so if
it's larger than VHOST_USER_MAX_CONFIG_SIZE, this is a programming
error. Turn the corresponding check into an assertion.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210609154658.350308-6-kwolf@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/hw/display/vhost-user-gpu.c b/hw/display/vhost-user-gpu.c
index 6cdaa1c73b..389199e6ca 100644
--- a/hw/display/vhost-user-gpu.c
+++ b/hw/display/vhost-user-gpu.c
@@ -415,14 +415,16 @@ vhost_user_gpu_get_config(VirtIODevice *vdev, uint8_t *config_data)
     VirtIOGPUBase *b = VIRTIO_GPU_BASE(vdev);
     struct virtio_gpu_config *vgconfig =
         (struct virtio_gpu_config *)config_data;
+    Error *local_err = NULL;
     int ret;
 
     memset(config_data, 0, sizeof(struct virtio_gpu_config));
 
     ret = vhost_dev_get_config(&g->vhost->dev,
-                               config_data, sizeof(struct virtio_gpu_config));
+                               config_data, sizeof(struct virtio_gpu_config),
+                               &local_err);
     if (ret) {
-        error_report("vhost-user-gpu: get device config space failed");
+        error_report_err(local_err);
         return;
     }