On Tue, 15 Jul 2025 at 05:37, Jason Wang <jasow...@redhat.com> wrote:
>
> From: Laurent Vivier <lviv...@redhat.com>
>
> This commit adds support for the vhost-user interface to the passt
> network backend, enabling high-performance, accelerated networking for
> guests using passt.
>
> The passt backend can now operate in a vhost-user mode, where it
> communicates with the guest's virtio-net device over a socket pair
> using the vhost-user protocol. This offloads the datapath from the
> main QEMU loop, significantly improving network performance.
>
> When the vhost-user=on option is used with -netdev passt, the new
> vhost initialization path is taken instead of the standard
> stream-based connection.
>
> Signed-off-by: Laurent Vivier <lviv...@redhat.com>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
Another couple of coverity issues:
> +static int passt_vhost_user_start(NetPasstState *s, VhostUserState *be)
> +{
> + struct vhost_net *net = NULL;
> + VhostNetOptions options;
> +
> + options.backend_type = VHOST_BACKEND_TYPE_USER;
> + options.net_backend = &s->data.nc;
> + options.opaque = be;
> + options.busyloop_timeout = 0;
> + options.nvqs = 2;
> + options.feature_bits = user_feature_bits;
> + options.max_tx_queue_size = VIRTQUEUE_MAX_SIZE;
> + options.get_acked_features = passt_get_acked_features;
> + options.save_acked_features = passt_save_acked_features;
> + options.is_vhost_user = true;
> +
> + net = vhost_net_init(&options);
> + if (!net) {
> + error_report("failed to init passt vhost_net");
> + goto err;
> + }
> +
> + if (s->vhost_net) {
> + vhost_net_cleanup(s->vhost_net);
> + g_free(s->vhost_net);
> + }
> + s->vhost_net = net;
> +
> + return 0;
> +err:
> + if (net) {
There is no path of code execution which can get here with
net not being NULL, so this code in the if() is dead. CID 1612371.
> + vhost_net_cleanup(net);
> + g_free(net);
> + }
> + passt_vhost_user_stop(s);
> + return -1;
> +}
> +
> +static void passt_vhost_user_event(void *opaque, QEMUChrEvent event)
> +{
> + NetPasstState *s = opaque;
> + Error *err = NULL;
We declare err here...
> +
> + switch (event) {
> + case CHR_EVENT_OPENED:
> + if (passt_vhost_user_start(s, s->vhost_user) < 0) {
> + qemu_chr_fe_disconnect(&s->vhost_chr);
> + return;
> + }
> + s->vhost_watch = qemu_chr_fe_add_watch(&s->vhost_chr, G_IO_HUP,
> + passt_vhost_user_watch, s);
> + net_client_set_link(&(NetClientState *){ &s->data.nc }, 1, true);
> + s->started = true;
> + break;
> + case CHR_EVENT_CLOSED:
> + if (s->vhost_watch) {
> + AioContext *ctx = qemu_get_current_aio_context();
> +
> + g_source_remove(s->vhost_watch);
> + s->vhost_watch = 0;
> + qemu_chr_fe_set_handlers(&s->vhost_chr, NULL, NULL, NULL, NULL,
> + NULL, NULL, false);
> +
> + aio_bh_schedule_oneshot(ctx, chr_closed_bh, s);
> + }
> + break;
> + case CHR_EVENT_BREAK:
> + case CHR_EVENT_MUX_IN:
> + case CHR_EVENT_MUX_OUT:
> + /* Ignore */
> + break;
> + }
...but we never use it in any of the event handling code..
> +
> + if (err) {
> + error_report_err(err);
...so this if() block is dead code. CID 1612375.
> + }
> +}
thanks
-- PMM
