diff --git a/include/qemu/help_option.h b/include/qemu/help_option.h
index 328d2a8..ca6389a 100644
--- a/include/qemu/help_option.h
+++ b/include/qemu/help_option.h
@@ -19,4 +19,15 @@
     return !strcmp(s, "?") || !strcmp(s, "help");
 }
 
+static inline int starts_with_help_option(const char *s)
+{
+    if (*s == '?') {
+        return 1;
+    }
+    if (g_str_has_prefix(s, "help")) {
+        return 4;
+    }
+    return 0;
+}
+
 #endif
diff --git a/include/qemu/option.h b/include/qemu/option.h
index 05e8a15..ac69352 100644
--- a/include/qemu/option.h
+++ b/include/qemu/option.h
@@ -149,6 +149,6 @@
 QemuOptsList *qemu_opts_append(QemuOptsList *dst, QemuOptsList *list);
 
 QDict *keyval_parse(const char *params, const char *implied_key,
-                    Error **errp);
+                    bool *help, Error **errp);
 
 #endif
diff --git a/qapi/qobject-input-visitor.c b/qapi/qobject-input-visitor.c
index f918a05..7b184b5 100644
--- a/qapi/qobject-input-visitor.c
+++ b/qapi/qobject-input-visitor.c
@@ -757,7 +757,7 @@
         assert(args);
         v = qobject_input_visitor_new(QOBJECT(args));
     } else {
-        args = keyval_parse(str, implied_key, errp);
+        args = keyval_parse(str, implied_key, NULL, errp);
         if (!args) {
             return NULL;
         }
diff --git a/storage-daemon/qemu-storage-daemon.c b/storage-daemon/qemu-storage-daemon.c
index 1ae1cda..6f0e0cf 100644
--- a/storage-daemon/qemu-storage-daemon.c
+++ b/storage-daemon/qemu-storage-daemon.c
@@ -278,7 +278,7 @@
                 }
                 qemu_opts_del(opts);
 
-                args = keyval_parse(optarg, "qom-type", &error_fatal);
+                args = keyval_parse(optarg, "qom-type", NULL, &error_fatal);
                 user_creatable_add_dict(args, true, &error_fatal);
                 qobject_unref(args);
                 break;
diff --git a/tests/test-keyval.c b/tests/test-keyval.c
index 04c62cf..ee927fe 100644
--- a/tests/test-keyval.c
+++ b/tests/test-keyval.c
@@ -27,27 +27,28 @@
     QDict *qdict, *sub_qdict;
     char long_key[129];
     char *params;
+    bool help;
 
     /* Nothing */
-    qdict = keyval_parse("", NULL, &error_abort);
+    qdict = keyval_parse("", NULL, NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 0);
     qobject_unref(qdict);
 
     /* Empty key (qemu_opts_parse() accepts this) */
-    qdict = keyval_parse("=val", NULL, &err);
+    qdict = keyval_parse("=val", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Empty key fragment */
-    qdict = keyval_parse(".", NULL, &err);
+    qdict = keyval_parse(".", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
-    qdict = keyval_parse("key.", NULL, &err);
+    qdict = keyval_parse("key.", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Invalid non-empty key (qemu_opts_parse() doesn't care) */
-    qdict = keyval_parse("7up=val", NULL, &err);
+    qdict = keyval_parse("7up=val", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
@@ -56,25 +57,25 @@
     long_key[127] = 'z';
     long_key[128] = 0;
     params = g_strdup_printf("k.%s=v", long_key);
-    qdict = keyval_parse(params + 2, NULL, &err);
+    qdict = keyval_parse(params + 2, NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Overlong key fragment */
-    qdict = keyval_parse(params, NULL, &err);
+    qdict = keyval_parse(params, NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
     g_free(params);
 
     /* Long key (qemu_opts_parse() accepts and truncates silently) */
     params = g_strdup_printf("k.%s=v", long_key + 1);
-    qdict = keyval_parse(params + 2, NULL, &error_abort);
+    qdict = keyval_parse(params + 2, NULL, NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 1);
     g_assert_cmpstr(qdict_get_try_str(qdict, long_key + 1), ==, "v");
     qobject_unref(qdict);
 
     /* Long key fragment */
-    qdict = keyval_parse(params, NULL, &error_abort);
+    qdict = keyval_parse(params, NULL, NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 1);
     sub_qdict = qdict_get_qdict(qdict, "k");
     g_assert(sub_qdict);
@@ -84,25 +85,25 @@
     g_free(params);
 
     /* Crap after valid key */
-    qdict = keyval_parse("key[0]=val", NULL, &err);
+    qdict = keyval_parse("key[0]=val", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Multiple keys, last one wins */
-    qdict = keyval_parse("a=1,b=2,,x,a=3", NULL, &error_abort);
+    qdict = keyval_parse("a=1,b=2,,x,a=3", NULL, NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 2);
     g_assert_cmpstr(qdict_get_try_str(qdict, "a"), ==, "3");
     g_assert_cmpstr(qdict_get_try_str(qdict, "b"), ==, "2,x");
     qobject_unref(qdict);
 
     /* Even when it doesn't in qemu_opts_parse() */
-    qdict = keyval_parse("id=foo,id=bar", NULL, &error_abort);
+    qdict = keyval_parse("id=foo,id=bar", NULL, NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 1);
     g_assert_cmpstr(qdict_get_try_str(qdict, "id"), ==, "bar");
     qobject_unref(qdict);
 
     /* Dotted keys */
-    qdict = keyval_parse("a.b.c=1,a.b.c=2,d=3", NULL, &error_abort);
+    qdict = keyval_parse("a.b.c=1,a.b.c=2,d=3", NULL, NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 2);
     sub_qdict = qdict_get_qdict(qdict, "a");
     g_assert(sub_qdict);
@@ -115,48 +116,48 @@
     qobject_unref(qdict);
 
     /* Inconsistent dotted keys */
-    qdict = keyval_parse("a.b=1,a=2", NULL, &err);
+    qdict = keyval_parse("a.b=1,a=2", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
-    qdict = keyval_parse("a.b=1,a.b.c=2", NULL, &err);
+    qdict = keyval_parse("a.b=1,a.b.c=2", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Trailing comma is ignored */
-    qdict = keyval_parse("x=y,", NULL, &error_abort);
+    qdict = keyval_parse("x=y,", NULL, NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 1);
     g_assert_cmpstr(qdict_get_try_str(qdict, "x"), ==, "y");
     qobject_unref(qdict);
 
     /* Except when it isn't */
-    qdict = keyval_parse(",", NULL, &err);
+    qdict = keyval_parse(",", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Value containing ,id= not misinterpreted as qemu_opts_parse() does */
-    qdict = keyval_parse("x=,,id=bar", NULL, &error_abort);
+    qdict = keyval_parse("x=,,id=bar", NULL, NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 1);
     g_assert_cmpstr(qdict_get_try_str(qdict, "x"), ==, ",id=bar");
     qobject_unref(qdict);
 
     /* Anti-social ID is left to caller (qemu_opts_parse() rejects it) */
-    qdict = keyval_parse("id=666", NULL, &error_abort);
+    qdict = keyval_parse("id=666", NULL, NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 1);
     g_assert_cmpstr(qdict_get_try_str(qdict, "id"), ==, "666");
     qobject_unref(qdict);
 
     /* Implied value not supported (unlike qemu_opts_parse()) */
-    qdict = keyval_parse("an,noaus,noaus=", NULL, &err);
+    qdict = keyval_parse("an,noaus,noaus=", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Implied value, key "no" (qemu_opts_parse(): negated empty key) */
-    qdict = keyval_parse("no", NULL, &err);
+    qdict = keyval_parse("no", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Implied key */
-    qdict = keyval_parse("an,aus=off,noaus=", "implied", &error_abort);
+    qdict = keyval_parse("an,aus=off,noaus=", "implied", NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 3);
     g_assert_cmpstr(qdict_get_try_str(qdict, "implied"), ==, "an");
     g_assert_cmpstr(qdict_get_try_str(qdict, "aus"), ==, "off");
@@ -164,7 +165,7 @@
     qobject_unref(qdict);
 
     /* Implied dotted key */
-    qdict = keyval_parse("val", "eins.zwei", &error_abort);
+    qdict = keyval_parse("val", "eins.zwei", NULL, &error_abort);
     g_assert_cmpuint(qdict_size(qdict), ==, 1);
     sub_qdict = qdict_get_qdict(qdict, "eins");
     g_assert(sub_qdict);
@@ -173,24 +174,81 @@
     qobject_unref(qdict);
 
     /* Implied key with empty value (qemu_opts_parse() accepts this) */
-    qdict = keyval_parse(",", "implied", &err);
+    qdict = keyval_parse(",", "implied", NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Likewise (qemu_opts_parse(): implied key with comma value) */
-    qdict = keyval_parse(",,,a=1", "implied", &err);
+    qdict = keyval_parse(",,,a=1", "implied", NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Implied key's value can't have comma (qemu_opts_parse(): it can) */
-    qdict = keyval_parse("val,,ue", "implied", &err);
+    qdict = keyval_parse("val,,ue", "implied", NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Empty key is not an implied key */
-    qdict = keyval_parse("=val", "implied", &err);
+    qdict = keyval_parse("=val", "implied", NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
+
+    /* "help" by itself, without implied key */
+    qdict = keyval_parse("help", NULL, &help, &error_abort);
+    g_assert_cmpuint(qdict_size(qdict), ==, 0);
+    g_assert(help);
+    qobject_unref(qdict);
+
+    /* "help" by itself, with implied key */
+    qdict = keyval_parse("help", "implied", &help, &error_abort);
+    g_assert_cmpuint(qdict_size(qdict), ==, 0);
+    g_assert(help);
+    qobject_unref(qdict);
+
+    /* "help" when no help is available, without implied key */
+    qdict = keyval_parse("help", NULL, NULL, &err);
+    error_free_or_abort(&err);
+    g_assert(!qdict);
+
+    /* "help" when no help is available, with implied key */
+    qdict = keyval_parse("help", "implied", NULL, &err);
+    error_free_or_abort(&err);
+    g_assert(!qdict);
+
+    /* Key "help" */
+    qdict = keyval_parse("help=on", NULL, &help, &error_abort);
+    g_assert_cmpuint(qdict_size(qdict), ==, 1);
+    g_assert_cmpstr(qdict_get_try_str(qdict, "help"), ==, "on");
+    g_assert(!help);
+    qobject_unref(qdict);
+
+    /* "help" followed by crap, without implied key */
+    qdict = keyval_parse("help.abc", NULL, &help, &err);
+    error_free_or_abort(&err);
+    g_assert(!qdict);
+
+    /* "help" followed by crap, with implied key */
+    qdict = keyval_parse("help.abc", "implied", &help, &err);
+    g_assert_cmpuint(qdict_size(qdict), ==, 1);
+    g_assert_cmpstr(qdict_get_try_str(qdict, "implied"), ==, "help.abc");
+    g_assert(!help);
+    qobject_unref(qdict);
+
+    /* "help" with other stuff, without implied key */
+    qdict = keyval_parse("number=42,help,foo=bar", NULL, &help, &error_abort);
+    g_assert_cmpuint(qdict_size(qdict), ==, 2);
+    g_assert_cmpstr(qdict_get_try_str(qdict, "number"), ==, "42");
+    g_assert_cmpstr(qdict_get_try_str(qdict, "foo"), ==, "bar");
+    g_assert(help);
+    qobject_unref(qdict);
+
+    /* "help" with other stuff, with implied key */
+    qdict = keyval_parse("val,help,foo=bar", "implied", &help, &error_abort);
+    g_assert_cmpuint(qdict_size(qdict), ==, 2);
+    g_assert_cmpstr(qdict_get_try_str(qdict, "implied"), ==, "val");
+    g_assert_cmpstr(qdict_get_try_str(qdict, "foo"), ==, "bar");
+    g_assert(help);
+    qobject_unref(qdict);
 }
 
 static void check_list012(QList *qlist)
@@ -215,26 +273,26 @@
     QDict *qdict, *sub_qdict;
 
     /* Root can't be a list */
-    qdict = keyval_parse("0=1", NULL, &err);
+    qdict = keyval_parse("0=1", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* List elements need not be in order */
-    qdict = keyval_parse("list.0=null,list.2=zwei,list.1=eins",
-                         NULL, &error_abort);
+    qdict = keyval_parse("list.0=null,list.2=zwei,list.1=eins", NULL, NULL,
+                         &error_abort);
     g_assert_cmpint(qdict_size(qdict), ==, 1);
     check_list012(qdict_get_qlist(qdict, "list"));
     qobject_unref(qdict);
 
     /* Multiple indexes, last one wins */
     qdict = keyval_parse("list.1=goner,list.0=null,list.01=eins,list.2=zwei",
-                         NULL, &error_abort);
+                         NULL, NULL, &error_abort);
     g_assert_cmpint(qdict_size(qdict), ==, 1);
     check_list012(qdict_get_qlist(qdict, "list"));
     qobject_unref(qdict);
 
     /* List at deeper nesting */
-    qdict = keyval_parse("a.list.1=eins,a.list.00=null,a.list.2=zwei",
+    qdict = keyval_parse("a.list.1=eins,a.list.00=null,a.list.2=zwei", NULL,
                          NULL, &error_abort);
     g_assert_cmpint(qdict_size(qdict), ==, 1);
     sub_qdict = qdict_get_qdict(qdict, "a");
@@ -243,18 +301,19 @@
     qobject_unref(qdict);
 
     /* Inconsistent dotted keys: both list and dictionary */
-    qdict = keyval_parse("a.b.c=1,a.b.0=2", NULL, &err);
+    qdict = keyval_parse("a.b.c=1,a.b.0=2", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
-    qdict = keyval_parse("a.0.c=1,a.b.c=2", NULL, &err);
+    qdict = keyval_parse("a.0.c=1,a.b.c=2", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 
     /* Missing list indexes */
-    qdict = keyval_parse("list.1=lonely", NULL, &err);
+    qdict = keyval_parse("list.1=lonely", NULL, NULL, &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
-    qdict = keyval_parse("list.0=null,list.2=eins,list.02=zwei", NULL, &err);
+    qdict = keyval_parse("list.0=null,list.2=eins,list.02=zwei", NULL, NULL,
+                         &err);
     error_free_or_abort(&err);
     g_assert(!qdict);
 }
@@ -266,7 +325,7 @@
     QDict *qdict;
     bool b;
 
-    qdict = keyval_parse("bool1=on,bool2=off", NULL, &error_abort);
+    qdict = keyval_parse("bool1=on,bool2=off", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -278,7 +337,7 @@
     visit_end_struct(v, NULL);
     visit_free(v);
 
-    qdict = keyval_parse("bool1=offer", NULL, &error_abort);
+    qdict = keyval_parse("bool1=offer", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -296,7 +355,7 @@
     uint64_t u;
 
     /* Lower limit zero */
-    qdict = keyval_parse("number1=0", NULL, &error_abort);
+    qdict = keyval_parse("number1=0", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -307,7 +366,7 @@
     visit_free(v);
 
     /* Upper limit 2^64-1 */
-    qdict = keyval_parse("number1=18446744073709551615,number2=-1",
+    qdict = keyval_parse("number1=18446744073709551615,number2=-1", NULL,
                          NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
@@ -321,8 +380,8 @@
     visit_free(v);
 
     /* Above upper limit */
-    qdict = keyval_parse("number1=18446744073709551616",
-                         NULL, &error_abort);
+    qdict = keyval_parse("number1=18446744073709551616", NULL, NULL,
+                         &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -332,8 +391,8 @@
     visit_free(v);
 
     /* Below lower limit */
-    qdict = keyval_parse("number1=-18446744073709551616",
-                         NULL, &error_abort);
+    qdict = keyval_parse("number1=-18446744073709551616", NULL, NULL,
+                         &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -343,8 +402,7 @@
     visit_free(v);
 
     /* Hex and octal */
-    qdict = keyval_parse("number1=0x2a,number2=052",
-                         NULL, &error_abort);
+    qdict = keyval_parse("number1=0x2a,number2=052", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -357,8 +415,7 @@
     visit_free(v);
 
     /* Trailing crap */
-    qdict = keyval_parse("number1=3.14,number2=08",
-                         NULL, &error_abort);
+    qdict = keyval_parse("number1=3.14,number2=08", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -378,7 +435,7 @@
     uint64_t sz;
 
     /* Lower limit zero */
-    qdict = keyval_parse("sz1=0", NULL, &error_abort);
+    qdict = keyval_parse("sz1=0", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -394,7 +451,7 @@
     qdict = keyval_parse("sz1=9007199254740991,"
                          "sz2=9007199254740992,"
                          "sz3=9007199254740993",
-                         NULL, &error_abort);
+                         NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -411,7 +468,7 @@
     /* Close to signed upper limit 0x7ffffffffffffc00 (53 msbs set) */
     qdict = keyval_parse("sz1=9223372036854774784," /* 7ffffffffffffc00 */
                          "sz2=9223372036854775295", /* 7ffffffffffffdff */
-                         NULL, &error_abort);
+                         NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -426,7 +483,7 @@
     /* Close to actual upper limit 0xfffffffffffff800 (53 msbs set) */
     qdict = keyval_parse("sz1=18446744073709549568," /* fffffffffffff800 */
                          "sz2=18446744073709550591", /* fffffffffffffbff */
-                         NULL, &error_abort);
+                         NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -441,7 +498,7 @@
     /* Beyond limits */
     qdict = keyval_parse("sz1=-1,"
                          "sz2=18446744073709550592", /* fffffffffffffc00 */
-                         NULL, &error_abort);
+                         NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -454,7 +511,7 @@
 
     /* Suffixes */
     qdict = keyval_parse("sz1=8b,sz2=1.5k,sz3=2M,sz4=0.1G,sz5=16777215T",
-                         NULL, &error_abort);
+                         NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -473,7 +530,7 @@
     visit_free(v);
 
     /* Beyond limit with suffix */
-    qdict = keyval_parse("sz1=16777216T", NULL, &error_abort);
+    qdict = keyval_parse("sz1=16777216T", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -483,7 +540,7 @@
     visit_free(v);
 
     /* Trailing crap */
-    qdict = keyval_parse("sz1=0Z,sz2=16Gi", NULL, &error_abort);
+    qdict = keyval_parse("sz1=0Z,sz2=16Gi", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -502,7 +559,7 @@
     QDict *qdict;
     int64_t i;
 
-    qdict = keyval_parse("a.b.c=1,a.b.c=2,d=3", NULL, &error_abort);
+    qdict = keyval_parse("a.b.c=1,a.b.c=2,d=3", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -520,7 +577,7 @@
     visit_end_struct(v, NULL);
     visit_free(v);
 
-    qdict = keyval_parse("a.b=", NULL, &error_abort);
+    qdict = keyval_parse("a.b=", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -542,7 +599,7 @@
     QDict *qdict;
     char *s;
 
-    qdict = keyval_parse("a.0=,a.1=I,a.2.0=II", NULL, &error_abort);
+    qdict = keyval_parse("a.0=,a.1=I,a.2.0=II", NULL, NULL, &error_abort);
     /* TODO empty list */
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
@@ -566,7 +623,7 @@
     visit_end_struct(v, NULL);
     visit_free(v);
 
-    qdict = keyval_parse("a.0=,b.0.0=head", NULL, &error_abort);
+    qdict = keyval_parse("a.0=,b.0.0=head", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -595,7 +652,7 @@
     bool present;
     int64_t i;
 
-    qdict = keyval_parse("a.b=1", NULL, &error_abort);
+    qdict = keyval_parse("a.b=1", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -631,7 +688,7 @@
      * the string variant if there is one, else an error.
      * TODO make it work for unambiguous cases like AltEnumBool below
      */
-    qdict = keyval_parse("a=1,b=2,c=on", NULL, &error_abort);
+    qdict = keyval_parse("a=1,b=2,c=on", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
@@ -655,7 +712,7 @@
     QList *qlist;
     QString *qstr;
 
-    qdict = keyval_parse("a.0=null,a.1=1", NULL, &error_abort);
+    qdict = keyval_parse("a.0=null,a.1=1", NULL, NULL, &error_abort);
     v = qobject_input_visitor_new_keyval(QOBJECT(qdict));
     qobject_unref(qdict);
     visit_start_struct(v, NULL, NULL, 0, &error_abort);
diff --git a/util/keyval.c b/util/keyval.c
index 8f33a36..7f625ad 100644
--- a/util/keyval.c
+++ b/util/keyval.c
@@ -14,10 +14,11 @@
  * KEY=VALUE,... syntax:
  *
  *   key-vals     = [ key-val { ',' key-val } [ ',' ] ]
- *   key-val      = key '=' val
+ *   key-val      = key '=' val | help
  *   key          = key-fragment { '.' key-fragment }
  *   key-fragment = / [^=,.]+ /
  *   val          = { / [^,]+ / | ',,' }
+ *   help         = 'help' | '?'
  *
  * Semantics defined by reduction to JSON:
  *
@@ -54,6 +55,9 @@
  *
  * The length of any key-fragment must be between 1 and 127.
  *
+ * If any key-val is help, the object is to be treated as a help
+ * request.
+ *
  * Design flaw: there is no way to denote an empty array or non-root
  * object.  While interpreting "key absent" as empty seems natural
  * (removing a key-val from the input string removes the member when
@@ -75,7 +79,7 @@
  *
  *   key-vals     = [ key-val-1st { ',' key-val } [ ',' ] ]
  *   key-val-1st  = val-no-key | key-val
- *   val-no-key   = / [^=,]+ /
+ *   val-no-key   = / [^=,]+ / - help
  *
  * where val-no-key is syntactic sugar for implied-key=val-no-key.
  *
@@ -89,6 +93,7 @@
 #include "qapi/qmp/qlist.h"
 #include "qapi/qmp/qstring.h"
 #include "qemu/cutils.h"
+#include "qemu/help_option.h"
 #include "qemu/option.h"
 
 /*
@@ -162,15 +167,20 @@
 }
 
 /*
- * Parse one KEY=VALUE from @params, store result in @qdict.
+ * Parse one parameter from @params.
+ *
+ * If we're looking at KEY=VALUE, store result in @qdict.
  * The first fragment of KEY applies to @qdict.  Subsequent fragments
  * apply to nested QDicts, which are created on demand.  @implied_key
  * is as in keyval_parse().
- * On success, return a pointer to the next KEY=VALUE, or else to '\0'.
+ *
+ * If we're looking at "help" or "?", set *help to true.
+ *
+ * On success, return a pointer to the next parameter, or else to '\0'.
  * On failure, return NULL.
  */
 static const char *keyval_parse_one(QDict *qdict, const char *params,
-                                    const char *implied_key,
+                                    const char *implied_key, bool *help,
                                     Error **errp)
 {
     const char *key, *key_end, *val_end, *s, *end;
@@ -184,11 +194,21 @@
     key = params;
     val_end = NULL;
     len = strcspn(params, "=,");
-    if (implied_key && len && key[len] != '=') {
-        /* Desugar implied key */
-        key = implied_key;
-        val_end = params + len;
-        len = strlen(implied_key);
+    if (len && key[len] != '=') {
+        if (starts_with_help_option(key) == len) {
+            *help = true;
+            s = key + len;
+            if (*s == ',') {
+                s++;
+            }
+            return s;
+        }
+        if (implied_key) {
+            /* Desugar implied key */
+            key = implied_key;
+            val_end = params + len;
+            len = strlen(implied_key);
+        }
     }
     key_end = key + len;
 
@@ -398,21 +418,32 @@
 
 /*
  * Parse @params in QEMU's traditional KEY=VALUE,... syntax.
+ *
  * If @implied_key, the first KEY= can be omitted.  @implied_key is
  * implied then, and VALUE can't be empty or contain ',' or '='.
+ *
+ * A parameter "help" or "?" without a value isn't added to the
+ * resulting dictionary, but instead is interpreted as help request.
+ * All other options are parsed and returned normally so that context
+ * specific help can be printed.
+ *
+ * If @p_help is not NULL, store whether help is requested there.
+ * If @p_help is NULL and help is requested, fail.
+ *
  * On success, return a dictionary of the parsed keys and values.
  * On failure, store an error through @errp and return NULL.
  */
 QDict *keyval_parse(const char *params, const char *implied_key,
-                    Error **errp)
+                    bool *p_help, Error **errp)
 {
     QDict *qdict = qdict_new();
     QObject *listified;
     const char *s;
+    bool help = false;
 
     s = params;
     while (*s) {
-        s = keyval_parse_one(qdict, s, implied_key, errp);
+        s = keyval_parse_one(qdict, s, implied_key, &help, errp);
         if (!s) {
             qobject_unref(qdict);
             return NULL;
@@ -420,6 +451,14 @@
         implied_key = NULL;
     }
 
+    if (p_help) {
+        *p_help = help;
+    } else if (help) {
+        error_setg(errp, "Help is not available for this option");
+        qobject_unref(qdict);
+        return NULL;
+    }
+
     listified = keyval_listify(qdict, NULL, errp);
     if (!listified) {
         qobject_unref(qdict);