On Thu, Jun 04, 2026 at 08:44:20PM +0800, Bin Guo wrote:
> vhost_virtqueue_start() unmasks the call notifier by calling
> vhost_virtqueue_mask(), whose vhost_set_vring_call ioctl can fail
> (closed vhost-user socket, kernel ENOMEM, revoked guest_notifier fd)
> but whose void signature throws the error away. vhost_dev_start()
> then reports success while the backend has no valid call eventfd for
> that vq, leaving the guest with a working kick path but no virtqueue
> interrupts -- a half-up state harder to diagnose than a clean failure.
>
> Make vhost_virtqueue_mask() return int and handle the error in the
> start path via the existing fail_vector unwind. Other callers reach
> the function through VirtioDeviceClass.guest_notifier_mask, whose
> void signature offers no upward error channel; they invoke it as a
> statement and remain source-compatible.
>
> Resolves a long-standing TODO at the unmask call.
>
> Signed-off-by: Bin Guo <[email protected]>
> ---
> hw/virtio/vhost.c | 12 +++++++++---
> include/hw/virtio/vhost.h | 4 ++--
> 2 files changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index b9dc4ed13b..42e2fc9952 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1351,8 +1351,11 @@ int vhost_virtqueue_start(struct vhost_dev *dev,
> * will do it later.
> */
> if (!vdev->use_guest_notifier_mask) {
> - /* TODO: check and handle errors. */
> - vhost_virtqueue_mask(dev, vdev, idx, false);
> + r = vhost_virtqueue_mask(dev, vdev, idx, false);
> + if (r < 0) {
> + /* No call eventfd means no interrupts; bail out. */
> + goto fail_vector;
> + }
> }
>
> if (k->query_guest_notifiers &&
Can you rebase please? Thanks!
> @@ -1815,7 +1818,7 @@ bool vhost_virtqueue_pending(struct vhost_dev *hdev,
> int n)
> }
>
> /* Mask/unmask events from this vq. */
> -void vhost_virtqueue_mask(struct vhost_dev *hdev, VirtIODevice *vdev, int n,
> +int vhost_virtqueue_mask(struct vhost_dev *hdev, VirtIODevice *vdev, int n,
> bool mask)
> {
> struct VirtQueue *vvq = virtio_get_queue(vdev, n);
> @@ -1836,7 +1839,10 @@ void vhost_virtqueue_mask(struct vhost_dev *hdev,
> VirtIODevice *vdev, int n,
> r = hdev->vhost_ops->vhost_set_vring_call(hdev, &file);
> if (r < 0) {
> error_report("vhost_set_vring_call failed %d", -r);
> + return r;
> }
> +
> + return 0;
> }
>
> bool vhost_config_pending(struct vhost_dev *hdev)
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index 89817bd848..96cc261822 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -317,8 +317,8 @@ bool vhost_virtqueue_pending(struct vhost_dev *hdev, int
> n);
>
> /* Mask/unmask events from this vq.
> */
> -void vhost_virtqueue_mask(struct vhost_dev *hdev, VirtIODevice *vdev, int n,
> - bool mask);
> +int vhost_virtqueue_mask(struct vhost_dev *hdev, VirtIODevice *vdev, int n,
> + bool mask);
>
> /**
> * vhost_get_features_ex() - sanitize the extended features set
> --
> 2.50.1 (Apple Git-155)
