vhost: Return 0/-errno in vhost_dev_init()

Instead of just returning 0/-1 and letting the caller make up a
meaningless error message, switch to 0/-errno so that different kinds of
errors can be distinguished in the caller.

This involves changing a few more callbacks in VhostOps to return
0/-errno: .vhost_set_owner(), .vhost_get_features() and
.vhost_virtqueue_set_busyloop_timeout(). The implementations of these
functions are trivial as they generally just send a message to the
backend.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210609154658.350308-4-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>

4 files changed, 17 insertions, 9 deletions

diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index f4f71cf..594d770 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -24,10 +24,12 @@ static int vhost_kernel_call(struct vhost_dev *dev, unsigned long int request,
                              void *arg)
 {
     int fd = (uintptr_t) dev->opaque;
+    int ret;
 
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_KERNEL);
 
-    return ioctl(fd, request, arg);
+    ret = ioctl(fd, request, arg);
+    return ret < 0 ? -errno : ret;
 }
 
 static int vhost_kernel_init(struct vhost_dev *dev, void *opaque, Error **errp)
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 024cb20..889559d 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -1353,7 +1353,11 @@ static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64)
 
 static int vhost_user_get_features(struct vhost_dev *dev, uint64_t *features)
 {
-    return vhost_user_get_u64(dev, VHOST_USER_GET_FEATURES, features);
+    if (vhost_user_get_u64(dev, VHOST_USER_GET_FEATURES, features) < 0) {
+        return -EPROTO;
+    }
+
+    return 0;
 }
 
 static int vhost_user_set_owner(struct vhost_dev *dev)
@@ -1364,7 +1368,7 @@ static int vhost_user_set_owner(struct vhost_dev *dev)
     };
 
     if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
-        return -1;
+        return -EPROTO;
     }
 
     return 0;
@@ -1872,7 +1876,7 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque,
 
     err = vhost_user_get_features(dev, &features);
     if (err < 0) {
-        return -EPROTO;
+        return err;
     }
 
     if (virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) {
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 80827ee..0f469f1 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -245,10 +245,12 @@ static int vhost_vdpa_call(struct vhost_dev *dev, unsigned long int request,
 {
     struct vhost_vdpa *v = dev->opaque;
     int fd = v->device_fd;
+    int ret;
 
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
 
-    return ioctl(fd, request, arg);
+    ret = ioctl(fd, request, arg);
+    return ret < 0 ? -errno : ret;
 }
 
 static void vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t status)
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index fd13135..c7f9d8b 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1309,13 +1309,13 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
 
     r = hdev->vhost_ops->vhost_set_owner(hdev);
     if (r < 0) {
-        error_setg(errp, "vhost_set_owner failed");
+        error_setg_errno(errp, -r, "vhost_set_owner failed");
         goto fail;
     }
 
     r = hdev->vhost_ops->vhost_get_features(hdev, &features);
     if (r < 0) {
-        error_setg(errp, "vhost_get_features failed");
+        error_setg_errno(errp, -r, "vhost_get_features failed");
         goto fail;
     }
 
@@ -1332,7 +1332,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
             r = vhost_virtqueue_set_busyloop_timeout(hdev, hdev->vq_index + i,
                                                      busyloop_timeout);
             if (r < 0) {
-                error_setg(errp, "Failed to set busyloop timeout");
+                error_setg_errno(errp, -r, "Failed to set busyloop timeout");
                 goto fail_busyloop;
             }
         }
@@ -1391,7 +1391,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     if (used_memslots > hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) {
         error_setg(errp, "vhost backend memory slots limit is less"
                    " than current number of present memory slots");
-        r = -1;
+        r = -EINVAL;
         goto fail_busyloop;
     }