On Mon, 26 Jun 2023 at 13:29, Michael S. Tsirkin <[email protected]> wrote:
>
> From: Eugenio Pérez <[email protected]>
>
> Evaluating it at start time instead of initialization time may make the
> guest capable of dynamically adding or removing migration blockers.
>
> Also, moving to initialization reduces the number of ioctls in the
> migration, reducing failure possibilities.
>
> As a drawback we need to check for CVQ isolation twice: one time with no
> MQ negotiated and another one acking it, as long as the device supports
> it. This is because Vring ASID / group management is based on vq
> indexes, but we don't know the index of CVQ before negotiating MQ.
I was looking at this code because of a Coverity report.
That turned out to be a false positive, but I did notice
something here that looks like it might be wrong:
>
> +/**
> + * Probe if CVQ is isolated
> + *
> + * @device_fd The vdpa device fd
> + * @features Features offered by the device.
> + * @cvq_index The control vq pair index
> + *
> + * Returns <0 in case of failure, 0 if false and 1 if true.
> + */
> +static int vhost_vdpa_probe_cvq_isolation(int device_fd, uint64_t features,
> + int cvq_index, Error **errp)
> +{
> + uint64_t backend_features;
> + int64_t cvq_group;
> + uint8_t status = VIRTIO_CONFIG_S_ACKNOWLEDGE |
> + VIRTIO_CONFIG_S_DRIVER |
> + VIRTIO_CONFIG_S_FEATURES_OK;
> + int r;
> +
> + ERRP_GUARD();
> +
> + r = ioctl(device_fd, VHOST_GET_BACKEND_FEATURES, &backend_features);
> + if (unlikely(r < 0)) {
> + error_setg_errno(errp, errno, "Cannot get vdpa backend_features");
> + return r;
> + }
> +
> + if (!(backend_features & BIT_ULL(VHOST_BACKEND_F_IOTLB_ASID))) {
> + return 0;
> + }
> +
> + r = ioctl(device_fd, VHOST_SET_FEATURES, &features);
> + if (unlikely(r)) {
> + error_setg_errno(errp, errno, "Cannot set features");
Shouldn't we have a 'return r' (or maybe a 'goto out') here ?
Otherwise we'll just plough onward and attempt to continue
execution...
> + }
> +
> + r = ioctl(device_fd, VHOST_VDPA_SET_STATUS, &status);
> + if (unlikely(r)) {
> + error_setg_errno(errp, -r, "Cannot set device features");
Isn't this trying to set device status, not features ?
> + goto out;
> + }
thanks
-- PMM
