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>

hw/block/vhost-user-blk.c

@@ -91,11 +91,13 @@ static int vhost_user_blk_handle_config_change(struct vhost_dev *dev)
     int ret;
     struct virtio_blk_config blkcfg;
     VHostUserBlk *s = VHOST_USER_BLK(dev->vdev);
+    Error *local_err = NULL;
 
     ret = vhost_dev_get_config(dev, (uint8_t *)&blkcfg,
-                               sizeof(struct virtio_blk_config));
+                               sizeof(struct virtio_blk_config),
+                               &local_err);
     if (ret < 0) {
-        error_report("get config space failed");
+        error_report_err(local_err);
         return -1;
     }
 
@@ -478,9 +480,8 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
     assert(s->connected);
 
     ret = vhost_dev_get_config(&s->dev, (uint8_t *)&s->blkcfg,
-                               sizeof(struct virtio_blk_config));
+                               sizeof(struct virtio_blk_config), errp);
     if (ret < 0) {
-        error_setg(errp, "vhost-user-blk: get block config failed");
         goto vhost_err;
     }
 

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;
     }
 

hw/input/vhost-user-input.c

@@ -49,13 +49,15 @@ static void vhost_input_get_config(VirtIODevice *vdev, uint8_t *config_data)
 {
     VirtIOInput *vinput = VIRTIO_INPUT(vdev);
     VHostUserInput *vhi = VHOST_USER_INPUT(vdev);
+    Error *local_err = NULL;
     int ret;
 
     memset(config_data, 0, vinput->cfg_size);
 
-    ret = vhost_dev_get_config(&vhi->vhost->dev, config_data, vinput->cfg_size);
+    ret = vhost_dev_get_config(&vhi->vhost->dev, config_data, vinput->cfg_size,
+                               &local_err);
     if (ret) {
-        error_report("vhost-user-input: get device config space failed");
+        error_report_err(local_err);
         return;
     }
 }

hw/net/vhost_net.c

@@ -117,7 +117,7 @@ uint64_t vhost_net_get_features(struct vhost_net *net, uint64_t features)
 int vhost_net_get_config(struct vhost_net *net,  uint8_t *config,
                          uint32_t config_len)
 {
-    return vhost_dev_get_config(&net->dev, config, config_len);
+    return vhost_dev_get_config(&net->dev, config, config_len, NULL);
 }
 int vhost_net_set_config(struct vhost_net *net, const uint8_t *data,
                          uint32_t offset, uint32_t size, uint32_t flags)

hw/virtio/vhost-user-vsock.c

@@ -34,10 +34,12 @@ static void vuv_get_config(VirtIODevice *vdev, uint8_t *config)
 static int vuv_handle_config_change(struct vhost_dev *dev)
 {
     VHostUserVSock *vsock = VHOST_USER_VSOCK(dev->vdev);
+    Error *local_err = NULL;
     int ret = vhost_dev_get_config(dev, (uint8_t *)&vsock->vsockcfg,
-                                   sizeof(struct virtio_vsock_config));
+                                   sizeof(struct virtio_vsock_config),
+                                   &local_err);
     if (ret < 0) {
-        error_report("get config space failed");
+        error_report_err(local_err);
         return -1;
     }
 
@@ -114,9 +116,8 @@ static void vuv_device_realize(DeviceState *dev, Error **errp)
     }
 
     ret = vhost_dev_get_config(&vvc->vhost_dev, (uint8_t *)&vsock->vsockcfg,
-                               sizeof(struct virtio_vsock_config));
+                               sizeof(struct virtio_vsock_config), errp);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "get config space failed");
         goto err_vhost_dev;
     }
 

hw/virtio/vhost-user.c

@@ -2117,7 +2117,7 @@ static void vhost_user_set_iotlb_callback(struct vhost_dev *dev, int enabled)
 }
 
 static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
-                                 uint32_t config_len)
+                                 uint32_t config_len, Error **errp)
 {
     VhostUserMsg msg = {
         .hdr.request = VHOST_USER_GET_CONFIG,
@@ -2127,32 +2127,32 @@ static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
 
     if (!virtio_has_feature(dev->protocol_features,
                 VHOST_USER_PROTOCOL_F_CONFIG)) {
-        return -1;
+        error_setg(errp, "VHOST_USER_PROTOCOL_F_CONFIG not supported");
+        return -EINVAL;
     }
 
-    if (config_len > VHOST_USER_MAX_CONFIG_SIZE) {
+    assert(config_len <= VHOST_USER_MAX_CONFIG_SIZE);
-        return -1;
-    }
 
     msg.payload.config.offset = 0;
     msg.payload.config.size = config_len;
     if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
-        return -1;
+        return -EPROTO;
     }
 
     if (vhost_user_read(dev, &msg) < 0) {
-        return -1;
+        return -EPROTO;
     }
 
     if (msg.hdr.request != VHOST_USER_GET_CONFIG) {
-        error_report("Received unexpected msg type. Expected %d received %d",
+        error_setg(errp,
-                     VHOST_USER_GET_CONFIG, msg.hdr.request);
+                   "Received unexpected msg type. Expected %d received %d",
-        return -1;
+                   VHOST_USER_GET_CONFIG, msg.hdr.request);
+        return -EINVAL;
     }
 
     if (msg.hdr.size != VHOST_USER_CONFIG_HDR_SIZE + config_len) {
-        error_report("Received bad msg size.");
+        error_setg(errp, "Received bad msg size.");
-        return -1;
+        return -EINVAL;
     }
 
     memcpy(config, msg.payload.config.region, config_len);

hw/virtio/vhost-vdpa.c

@@ -523,7 +523,7 @@ static int vhost_vdpa_set_config(struct vhost_dev *dev, const uint8_t *data,
 }
 
 static int vhost_vdpa_get_config(struct vhost_dev *dev, uint8_t *config,
-                                   uint32_t config_len)
+                                   uint32_t config_len, Error **errp)
 {
     struct vhost_vdpa_config *v_config;
     unsigned long config_size = offsetof(struct vhost_vdpa_config, buf);

hw/virtio/vhost.c

@@ -1562,15 +1562,23 @@ void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits,
 }
 
 int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
-                         uint32_t config_len)
+                         uint32_t config_len, Error **errp)
 {
+    ERRP_GUARD();
+    int ret;
+
     assert(hdev->vhost_ops);
 
     if (hdev->vhost_ops->vhost_get_config) {
-        return hdev->vhost_ops->vhost_get_config(hdev, config, config_len);
+        ret = hdev->vhost_ops->vhost_get_config(hdev, config, config_len, errp);
+        if (ret < 0 && !*errp) {
+            error_setg_errno(errp, -ret, "vhost_get_config failed");
+        }
+        return ret;
     }
 
-    return -1;
+    error_setg(errp, "vhost_get_config not implemented");
+    return -ENOTSUP;
 }
 
 int vhost_dev_set_config(struct vhost_dev *hdev, const uint8_t *data,

include/hw/virtio/vhost-backend.h

@@ -98,7 +98,7 @@ typedef int (*vhost_set_config_op)(struct vhost_dev *dev, const uint8_t *data,
                                    uint32_t offset, uint32_t size,
                                    uint32_t flags);
 typedef int (*vhost_get_config_op)(struct vhost_dev *dev, uint8_t *config,
-                                   uint32_t config_len);
+                                   uint32_t config_len, Error **errp);
 
 typedef int (*vhost_crypto_create_session_op)(struct vhost_dev *dev,
                                               void *session_info,

include/hw/virtio/vhost.h

@@ -130,8 +130,8 @@ int vhost_net_set_backend(struct vhost_dev *hdev,
                           struct vhost_vring_file *file);
 
 int vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write);
-int vhost_dev_get_config(struct vhost_dev *dev, uint8_t *config,
+int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
-                         uint32_t config_len);
+                         uint32_t config_len, Error **errp);
 int vhost_dev_set_config(struct vhost_dev *dev, const uint8_t *data,
                          uint32_t offset, uint32_t size, uint32_t flags);
 /* notifier callback in case vhost device config space changed