Re: [RFC PATCH v4 03/11] qapi: net: introduce a way to bypass qemu_opts_parse_noisily()

[Markus Armbruster]

Laurent Vivier <lvivier@redhat.com> writes:

> As qemu_opts_parse_noisily() flattens the QAPI structures ("type" field
> of Netdev structure can collides with "type" field of SocketAddress),
> we introduce a way to bypass qemu_opts_parse_noisily() and use directly
> visit_type_Netdev() to parse the backend parameters.
>
> More details from Markus:
>
> qemu_init() passes the argument of -netdev, -nic, and -net to
> net_client_parse().
>
> net_client_parse() parses with qemu_opts_parse_noisily(), passing
> QemuOptsList qemu_netdev_opts for -netdev, qemu_nic_opts for -nic, and
> qemu_net_opts for -net.  Their desc[] are all empty, which means any
> keys are accepted.  The result of the parse (a QemuOpts) is stored in
> the QemuOptsList.
>
> Note that QemuOpts is flat by design.  In some places, we layer non-flat
> on top using dotted keys convention, but not here.
>
> net_init_clients() iterates over the stored QemuOpts, and passes them to
> net_init_netdev(), net_param_nic(), or net_init_client(), respectively.
>
> These functions pass the QemuOpts to net_client_init().  They also do
> other things with the QemuOpts, which we can ignore here.
>
> net_client_init() uses the opts visitor to convert the (flat) QemOpts to
> a (non-flat) QAPI object Netdev.  Netdev is also the argument of QMP
> command netdev_add.
>
> The opts visitor was an early attempt to support QAPI in
> (QemuOpts-based) CLI.  It restricts QAPI types to a certain shape; see
> commit eb7ee2cbeb "qapi: introduce OptsVisitor".
>
> A more modern way to support QAPI is qobject_input_visitor_new_str().
> It uses keyval_parse() instead of QemuOpts for KEY=VALUE,... syntax, and
> it also supports JSON syntax.  The former isn't quite as expressive as
> JSON, but it's a lot closer than QemuOpts + opts visitor.
>
> This commit paves the way to use of the modern way instead.
>
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>  include/net/net.h |  4 +++-
>  net/net.c         | 60 +++++++++++++++++++++++++++++++++++++++++++----
>  softmmu/vl.c      | 14 +++++------
>  3 files changed, 65 insertions(+), 13 deletions(-)
>
> diff --git a/include/net/net.h b/include/net/net.h
> index c53c64ac18c4..826e14a78734 100644
> --- a/include/net/net.h
> +++ b/include/net/net.h
> @@ -214,7 +214,9 @@ extern NICInfo nd_table[MAX_NICS];
>  extern const char *host_net_devices[];
>  
>  /* from net.c */
> -int net_client_parse(QemuOptsList *opts_list, const char *str);
> +bool netdev_is_modern(const char *optarg);
> +void netdev_parse_modern(const char *optarg);
> +void net_client_parse(QemuOptsList *opts_list, const char *str);
>  void show_netdevs(void);
>  void net_init_clients(void);
>  void net_check_clients(void);
> diff --git a/net/net.c b/net/net.c
> index 15958f881776..531e6c5d2056 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -54,6 +54,7 @@
>  #include "net/colo-compare.h"
>  #include "net/filter.h"
>  #include "qapi/string-output-visitor.h"
> +#include "qapi/qobject-input-visitor.h"
>  
>  /* Net bridge is currently not supported for W32. */
>  #if !defined(_WIN32)
> @@ -63,6 +64,16 @@
>  static VMChangeStateEntry *net_change_state_entry;
>  static QTAILQ_HEAD(, NetClientState) net_clients;
>  
> +typedef struct NetdevQueueEntry {
> +    Netdev *nd;
> +    Location loc;
> +    QSIMPLEQ_ENTRY(NetdevQueueEntry) entry;
> +} NetdevQueueEntry;
> +
> +typedef QSIMPLEQ_HEAD(, NetdevQueueEntry) NetdevQueue;
> +
> +static NetdevQueue nd_queue = QSIMPLEQ_HEAD_INITIALIZER(nd_queue);
> +
>  /***********************************************************/
>  /* network device redirectors */
>  
> @@ -1562,6 +1573,20 @@ out:
>      return ret;
>  }
>  
> +static void netdev_init_modern(void)
> +{
> +    while (!QSIMPLEQ_EMPTY(&nd_queue)) {
> +        NetdevQueueEntry *nd = QSIMPLEQ_FIRST(&nd_queue);
> +
> +        QSIMPLEQ_REMOVE_HEAD(&nd_queue, entry);
> +        loc_push_restore(&nd->loc);
> +        net_client_init1(nd->nd, true, &error_fatal);
> +        loc_pop(&nd->loc);
> +        qapi_free_Netdev(nd->nd);
> +        g_free(nd);
> +    }
> +}
> +
>  void net_init_clients(void)
>  {
>      net_change_state_entry =
> @@ -1569,6 +1594,8 @@ void net_init_clients(void)
>  
>      QTAILQ_INIT(&net_clients);
>  
> +    netdev_init_modern();
> +
>      qemu_opts_foreach(qemu_find_opts("netdev"), net_init_netdev, NULL,
>                        &error_fatal);
>  
> @@ -1579,13 +1606,38 @@ void net_init_clients(void)
>                        &error_fatal);
>  }
>  
> -int net_client_parse(QemuOptsList *opts_list, const char *optarg)
> +/*
> + * netdev_is_modern() returns true when the backend needs to bypass
> + * qemu_opts_parse_noisily()
> + */

Suggest

   /*
    * Does this -netdev argument use modern rather than traditional syntax?
    * Modern syntax is to be parsed with netdev_parse_modern().
    * Traditional syntax is to be parsed with net_client_parse().
    */

> +bool netdev_is_modern(const char *optarg)
> +{
> +    return false;
> +}
> +
> +/*
> + * netdev_parse_modern() uses modern, more expressive syntax than
> + * net_client_parse(), supports only the netdev option.

Suggest "but supports" or "and supports".

Suggest "the -netdev option".

Should we mention the difference in storing of the result?
netdev_parse_modern() appends to @nd_queue, whereas net_client_parse()
appends to @qemu_netdev_opts.

> + */
> +void netdev_parse_modern(const char *optarg)
> +{
> +    Visitor *v;
> +    NetdevQueueEntry *nd;
> +
> +    v = qobject_input_visitor_new_str(optarg, "type", &error_fatal);
> +    nd = g_new(NetdevQueueEntry, 1);
> +    visit_type_Netdev(v, NULL, &nd->nd, &error_fatal);
> +    visit_free(v);
> +    loc_save(&nd->loc);
> +
> +    QSIMPLEQ_INSERT_TAIL(&nd_queue, nd, entry);
> +}
> +
> +void net_client_parse(QemuOptsList *opts_list, const char *optarg)
>  {
>      if (!qemu_opts_parse_noisily(opts_list, optarg, true)) {
> -        return -1;
> +        exit(1);
>      }
> -
> -    return 0;
>  }

I'd put the change of net_client_parse() into its own patch.

>  
>  /* From FreeBSD */
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index c244e8afc4cc..f557e2d8cb8a 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -2794,21 +2794,19 @@ void qemu_init(int argc, char **argv, char **envp)
>                  break;
>              case QEMU_OPTION_netdev:
>                  default_net = 0;
> -                if (net_client_parse(qemu_find_opts("netdev"), optarg) == 
> -1) {
> -                    exit(1);
> +                if (netdev_is_modern(optarg)) {
> +                    netdev_parse_modern(optarg);
> +                } else {
> +                    net_client_parse(qemu_find_opts("netdev"), optarg);
>                  }
>                  break;
>              case QEMU_OPTION_nic:
>                  default_net = 0;
> -                if (net_client_parse(qemu_find_opts("nic"), optarg) == -1) {
> -                    exit(1);
> -                }
> +                net_client_parse(qemu_find_opts("nic"), optarg);
>                  break;
>              case QEMU_OPTION_net:
>                  default_net = 0;
> -                if (net_client_parse(qemu_find_opts("net"), optarg) == -1) {
> -                    exit(1);
> -                }
> +                net_client_parse(qemu_find_opts("net"), optarg);
>                  break;
>  #ifdef CONFIG_LIBISCSI
>              case QEMU_OPTION_iscsi: