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qemu-option: restrict qemu_opts_set to merge-lists QemuOpts
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qemu_opts_set is used to create default network backends and to
parse sugar options -kernel, -initrd, -append, -bios and -dtb.
These are very different uses:

I would *expect* a function named qemu_opts_set to set an option in a
merge-lists QemuOptsList, such as -kernel, and possibly to set an option
in a non-merge-lists QemuOptsList with non-NULL id, similar to -set.

However, it wouldn't *work* to use qemu_opts_set for the latter
because qemu_opts_set uses fail_if_exists==1. So, for non-merge-lists
QemuOptsList and non-NULL id, the semantics of qemu_opts_set (fail if the
(QemuOptsList, id) pair already exists) are debatable.

On the other hand, I would not expect qemu_opts_set to create a
non-merge-lists QemuOpts with a single option; which it does, though.
For this case of non-merge-lists QemuOptsList and NULL id, qemu_opts_set
hardly adds value over qemu_opts_parse.  It does skip some parsing and
unescaping, but that's not needed when creating default network
backends.

So qemu_opts_set has warty behavior for non-merge-lists QemuOptsList
if id is non-NULL, and it's mostly pointless if id is NULL.  My
solution to keeping the API as simple as possible is to limit
qemu_opts_set to merge-lists QemuOptsList.  For them, it's useful (we
don't want comma-unescaping for -kernel) *and* has sane semantics.
Network backend creation is switched to qemu_opts_parse.

qemu_opts_set is now only used on merge-lists QemuOptsList... except
in the testcase, which is changed to use a merge-list QemuOptsList.

With this change we can also remove the id parameter.  With the
parameter always NULL, we know that qemu_opts_create cannot fail
and can pass &error_abort to it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@bonzini
bonzini committed Dec 10, 2020
1 parent 4d2c17b commit 32c02fd
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Showing 4 changed files with 28 additions and 23 deletions.
3 changes: 1 addition & 2 deletions include/qemu/option.h
View file
Expand Up @@ -119,8 +119,7 @@ QemuOpts *qemu_opts_create(QemuOptsList *list, const char *id,
int fail_if_exists, Error **errp);
void qemu_opts_reset(QemuOptsList *list);
void qemu_opts_loc_restore(QemuOpts *opts);
bool qemu_opts_set(QemuOptsList *list, const char *id,
const char *name, const char *value, Error **errp);
bool qemu_opts_set(QemuOptsList *list, const char *name, const char *value, Error **errp);
const char *qemu_opts_id(QemuOpts *opts);
void qemu_opts_set_id(QemuOpts *opts, char *id);
void qemu_opts_del(QemuOpts *opts);
Expand Down
19 changes: 7 additions & 12 deletions softmmu/vl.c
View file
Expand Up @@ -3388,20 +3388,16 @@ void qemu_init(int argc, char **argv, char **envp)
}
break;
case QEMU_OPTION_kernel:
qemu_opts_set(qemu_find_opts("machine"), NULL, "kernel", optarg,
&error_abort);
qemu_opts_set(qemu_find_opts("machine"), "kernel", optarg, &error_abort);
break;
case QEMU_OPTION_initrd:
qemu_opts_set(qemu_find_opts("machine"), NULL, "initrd", optarg,
&error_abort);
qemu_opts_set(qemu_find_opts("machine"), "initrd", optarg, &error_abort);
break;
case QEMU_OPTION_append:
qemu_opts_set(qemu_find_opts("machine"), NULL, "append", optarg,
&error_abort);
qemu_opts_set(qemu_find_opts("machine"), "append", optarg, &error_abort);
break;
case QEMU_OPTION_dtb:
qemu_opts_set(qemu_find_opts("machine"), NULL, "dtb", optarg,
&error_abort);
qemu_opts_set(qemu_find_opts("machine"), "dtb", optarg, &error_abort);
break;
case QEMU_OPTION_cdrom:
drive_add(IF_DEFAULT, 2, optarg, CDROM_OPTS);
Expand Down Expand Up @@ -3511,8 +3507,7 @@ void qemu_init(int argc, char **argv, char **envp)
}
break;
case QEMU_OPTION_bios:
qemu_opts_set(qemu_find_opts("machine"), NULL, "firmware", optarg,
&error_abort);
qemu_opts_set(qemu_find_opts("machine"), "firmware", optarg, &error_abort);
break;
case QEMU_OPTION_singlestep:
singlestep = 1;
Expand Down Expand Up @@ -4395,9 +4390,9 @@ void qemu_init(int argc, char **argv, char **envp)

if (default_net) {
QemuOptsList *net = qemu_find_opts("net");
qemu_opts_set(net, NULL, "type", "nic", &error_abort);
qemu_opts_parse(net, "nic", true, &error_abort);
#ifdef CONFIG_SLIRP
qemu_opts_set(net, NULL, "type", "user", &error_abort);
qemu_opts_parse(net, "user", true, &error_abort);
#endif
}

Expand Down
20 changes: 17 additions & 3 deletions tests/test-qemu-opts.c
View file
Expand Up @@ -84,11 +84,25 @@ static QemuOptsList opts_list_03 = {
},
};

static QemuOptsList opts_list_04 = {
.name = "opts_list_04",
.head = QTAILQ_HEAD_INITIALIZER(opts_list_04.head),
.merge_lists = true,
.desc = {
{
.name = "str3",
.type = QEMU_OPT_STRING,
},
{ /* end of list */ }
},
};

static void register_opts(void)
{
qemu_add_opts(&opts_list_01);
qemu_add_opts(&opts_list_02);
qemu_add_opts(&opts_list_03);
qemu_add_opts(&opts_list_04);
}

static void test_find_unknown_opts(void)
Expand Down Expand Up @@ -402,17 +416,17 @@ static void test_qemu_opts_set(void)
QemuOpts *opts;
const char *opt;

list = qemu_find_opts("opts_list_01");
list = qemu_find_opts("opts_list_04");
g_assert(list != NULL);
g_assert(QTAILQ_EMPTY(&list->head));
g_assert_cmpstr(list->name, ==, "opts_list_01");
g_assert_cmpstr(list->name, ==, "opts_list_04");

/* should not find anything at this point */
opts = qemu_opts_find(list, NULL);
g_assert(opts == NULL);

/* implicitly create opts and set str3 value */
qemu_opts_set(list, NULL, "str3", "value", &error_abort);
qemu_opts_set(list, "str3", "value", &error_abort);
g_assert(!QTAILQ_EMPTY(&list->head));

/* get the just created opts */
Expand Down
9 changes: 3 additions & 6 deletions util/qemu-option.c
View file
Expand Up @@ -670,15 +670,12 @@ void qemu_opts_loc_restore(QemuOpts *opts)
loc_restore(&opts->loc);
}

bool qemu_opts_set(QemuOptsList *list, const char *id,
const char *name, const char *value, Error **errp)
bool qemu_opts_set(QemuOptsList *list, const char *name, const char *value, Error **errp)
{
QemuOpts *opts;

opts = qemu_opts_create(list, id, 1, errp);
if (!opts) {
return false;
}
assert(list->merge_lists);
opts = qemu_opts_create(list, NULL, 0, &error_abort);
return qemu_opt_set(opts, name, value, errp);
}

Expand Down

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