Laurent Vivier <lviv...@redhat.com> writes: > On 13/05/2022 13:21, Markus Armbruster wrote: >> Laurent Vivier <lviv...@redhat.com> writes: >> >>> As qemu_opts_parse_noisily() flattens the QAPI structures ("type" field >>> of Netdev structure can collides with "type" field of SocketAddress), >> >> To remember how this works, I have to write a more verbose version of >> the above. Why not post it then, so here goes. >> >> 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. >> >>> we introduce a way to bypass qemu_opts_parse_noisily() and use directly >>> visit_type_Netdev() to parse the backend parameters. >> >> This commit paves the way to use of the modern way instead. > > I'm going to copy your analysis to the commit message of the patch.
Go right ahead :) >>> Signed-off-by: Laurent Vivier <lviv...@redhat.com> >>> --- >>> net/net.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ >>> 1 file changed, 54 insertions(+) >>> >>> diff --git a/net/net.c b/net/net.c >>> index 58c05c200622..2aab7167316c 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 +64,17 @@ >>> static VMChangeStateEntry *net_change_state_entry; >>> static QTAILQ_HEAD(, NetClientState) net_clients; >>> >>> +typedef struct NetdevQueueEntry { >>> + bool is_netdev; >>> + 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 */ >>> >>> @@ -1559,6 +1571,19 @@ int net_init_clients(Error **errp) >>> >>> QTAILQ_INIT(&net_clients); >>> >>> + while (!QSIMPLEQ_EMPTY(&nd_queue)) { >>> + NetdevQueueEntry *nd = QSIMPLEQ_FIRST(&nd_queue); >>> + >>> + QSIMPLEQ_REMOVE_HEAD(&nd_queue, entry); >>> + loc_push_restore(&nd->loc); >>> + if (net_client_init1(nd->nd, nd->is_netdev, errp) < 0) { >> >> I think you need to loc_pop() here. >> >>> + return -1; >>> + } >> >> Since the only caller passes &error_fatal, I'd be tempted to ditch the >> @errp argument, and simply do >> >> net_client_init1(nd->nd, nd->is_netdev, &error_fatal); >> >> It's what we do for -blockdev, -device, and -object. > > I've added a patch to remove the @errp from the net_init_clients() arguments. > >> >>> + loc_pop(&nd->loc); >>> + qapi_free_Netdev(nd->nd); >>> + g_free(nd); >>> + } >>> + >>> if (qemu_opts_foreach(qemu_find_opts("netdev"), >>> net_init_netdev, NULL, errp)) { >>> return -1; >>> @@ -1575,8 +1600,37 @@ int net_init_clients(Error **errp) >>> return 0; >>> } >>> >>> +/* >>> + * netdev_is_modern() returns true when the backend needs to bypass >>> + * qemu_opts_parse_noisily() >>> + */ >>> +static bool netdev_is_modern(const char *optarg) >>> +{ >>> + return false; >>> +} >>> + >>> int net_client_parse(QemuOptsList *opts_list, const char *optarg) >>> { >>> + if (netdev_is_modern(optarg)) { >>> + /* >>> + * We need to bypass qemu_opts_parse_noisily() to accept >>> + * new style object like addr.type=inet in SocketAddress >>> + */ >> >> I'm not sure this will makes sense to future readers. >> >> What about "Use modern, more expressive syntax"? > > Done. > >> >>> + 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); >>> + nd->is_netdev = strcmp(opts_list->name, "netdev") == 0; >>> + >>> + QSIMPLEQ_INSERT_TAIL(&nd_queue, nd, entry); >>> + return 0; >>> + } >> >> Matches what we do for -blockdev, except we additionally have >> nd->is_netdev. We need it for calling net_client_init1(). >> >> If netdev_is_modern(optarg), then the only use of parameter @opts_list >> is opts_list->name in the initialization of nd->is_netdev. >> >> There's a bit of code smell, I'm afraid. > > I don't see what is the problem. The function's signature int net_client_parse(QemuOptsList *opts_list, const char *optarg) suggests we're parsing @optarg into @opts_list. We do only if !netdev_is_modern(optarg). In other words, the function's actual behavior doesn't match reasonable expectations based on signature. A function comment would mitigate. If nd->is_netdev wasn't needed, we could code all this just like -blockdev. I think that would be simpler. >> I believe @is_netdev needs to be true for -netdev, -nic, and netdev_add; >> false for -net. >> >> Will we ever use the modern syntax with -net? > > Yes, I think we should support the same syntax with -netdev and -net. > > My first iteration was to pass is_netdev=true to net_client_init1() and > Stefano reported a > problem with "-net" with things like that: > > -net > dgram,id=socket0,local.type=inet,local.host=localhost,local.port=1234,\ > > remote.type=inet,remote.host=localhost,remote.port=1235 > -net nic,model=virtio,macaddr=9a:2b:2c:2d:2e:2f > >> >> Any chance we can deprecate -net? > > Who can decide of that? Thomas, I think you've done some work to replace use cases of -net. Do you know what's left? >>> + >>> if (!qemu_opts_parse_noisily(opts_list, optarg, true)) { >>> return -1; >>> } >> > > Thanks, > Laurent