Re: [Qemu-devel] [PATCH V2] net: don't use set/get_pointer() in set/get_netdev()

[Markus Armbruster]

Jason Wang <address@hidden> writes:

> Commit 1ceef9f27359cbe92ef124bf74de6f792e71f6fb (net: multiqueue
> support) tries to use set_pointer() and get_pointer() to set and get
> NICPeers which is not a pointer defined in DEFINE_PROP_NETDEV. This
> trick works but result a unclean and fragile implementation (e.g
> print_netdev and parse_netdev).
>
> This patch solves this issue by not using set/get_pinter() and set and
> get netdev directly in set_netdev() and get_netdev(). After this the
> parse_netdev() and print_netdev() were no longer used and dropped from
> the source.
>
> Cc: Markus Armbruster <address@hidden>
> Cc: Stefan Hajnoczi <address@hidden>
> Cc: Peter Maydell <address@hidden>
> Signed-off-by: Jason Wang <address@hidden>
> ---
> Changes from V1:
> - validate ncs pointer before accessing them, this fixes the qtest failure
>   on arm.
> ---
>  hw/core/qdev-properties-system.c | 71 
> ++++++++++++++++++++++------------------
>  1 file changed, 39 insertions(+), 32 deletions(-)
>
> diff --git a/hw/core/qdev-properties-system.c 
> b/hw/core/qdev-properties-system.c
> index ae0900f..6939ea5 100644
> --- a/hw/core/qdev-properties-system.c
> +++ b/hw/core/qdev-properties-system.c
> @@ -176,41 +176,67 @@ PropertyInfo qdev_prop_chr = {
>  };
>  
>  /* --- netdev device --- */
> +static void get_netdev(Object *obj, Visitor *v, void *opaque,
> +                       const char *name, Error **errp)
> +{
> +    DeviceState *dev = DEVICE(obj);
> +    Property *prop = opaque;
> +    NICPeers *peers_ptr = qdev_get_prop_ptr(dev, prop);
> +    char *p = g_strdup(peers_ptr->ncs[0] ? peers_ptr->ncs[0]->name : "");

Can ->ncs[0]->name ever be null?

>  
> -static int parse_netdev(DeviceState *dev, const char *str, void **ptr)
> +    visit_type_str(v, &p, name, errp);
> +    g_free(p);
> +}
> +
> +static void set_netdev(Object *obj, Visitor *v, void *opaque,
> +                       const char *name, Error **errp)
>  {
> -    NICPeers *peers_ptr = (NICPeers *)ptr;
> +    DeviceState *dev = DEVICE(obj);
> +    Property *prop = opaque;
> +    NICPeers *peers_ptr = qdev_get_prop_ptr(dev, prop);
>      NetClientState **ncs = peers_ptr->ncs;
>      NetClientState *peers[MAX_QUEUE_NUM];
> -    int queues, i = 0;
> -    int ret;
> +    Error *local_err = NULL;
> +    int err, queues, i = 0;
> +    char *str;
> +
> +    if (dev->realized) {
> +        qdev_prop_set_after_realize(dev, name, errp);
> +        return;
> +    }
> +
> +    visit_type_str(v, &str, name, &local_err);
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +        return;
> +    }
>  
>      queues = qemu_find_net_clients_except(str, peers,
>                                            NET_CLIENT_OPTIONS_KIND_NIC,
>                                            MAX_QUEUE_NUM);
>      if (queues == 0) {
> -        ret = -ENOENT;
> +        err = -ENOENT;
>          goto err;
>      }
>  
>      if (queues > MAX_QUEUE_NUM) {
> -        ret = -E2BIG;
> +        err = -E2BIG;

error_set_from_qdev_prop_error() does not accept -E2BIG.

You could call error_setg(...) directly instead.

>          goto err;
>      }
>  
>      for (i = 0; i < queues; i++) {
>          if (peers[i] == NULL) {
> -            ret = -ENOENT;
> +            err = -ENOENT;
>              goto err;
>          }
>  
>          if (peers[i]->peer) {
> -            ret = -EEXIST;
> +            err = -EEXIST;
>              goto err;
>          }
>  
>          if (ncs[i]) {
> -            ret = -EINVAL;
> +            err = -EINVAL;

error_set_from_qdev_prop_error() does not accept -EINVAL, either.

>              goto err;
>          }
>  
> @@ -219,31 +245,12 @@ static int parse_netdev(DeviceState *dev, const char 
> *str, void **ptr)
>      }
>  
>      peers_ptr->queues = queues;
> -
> -    return 0;
> +    g_free(str);
> +    return;
>  
>  err:

Label err clashes with local variable err.  Harmless, but maybe you'd
like to rename one of them.

> -    return ret;
> -}
> -
> -static char *print_netdev(void *ptr)
> -{
> -    NetClientState *netdev = ptr;
> -    const char *val = netdev->name ? netdev->name : "";
> -
> -    return g_strdup(val);
> -}
> -
> -static void get_netdev(Object *obj, Visitor *v, void *opaque,
> -                       const char *name, Error **errp)
> -{
> -    get_pointer(obj, v, opaque, print_netdev, name, errp);
> -}
> -
> -static void set_netdev(Object *obj, Visitor *v, void *opaque,
> -                       const char *name, Error **errp)
> -{
> -    set_pointer(obj, v, opaque, parse_netdev, name, errp);
> +    error_set_from_qdev_prop_error(errp, err, dev, prop, str);
> +    g_free(str);
>  }
>  
>  PropertyInfo qdev_prop_netdev = {

Instead of

        g_free(str);
        return;

    err:
        error_set_from_qdev_prop_error(errp, err, dev, prop, str);
        g_free(str);
    }

You could exploit that error_set_from_qdev_prop_error() does nothing
when err is 0:

    out:
        g_free(str);
        error_set_from_qdev_prop_error(errp, err, dev, prop, str);
        g_free(str);
    }