Re: [PATCH v2 1/1] util/async-teardown: wire up query-command-line-options

[Thomas Huth <thuth@redhat.com>]

On 20/03/2023 16.31, Markus Armbruster wrote:
> Claudio Imbrenda <imbrenda@linux.ibm.com> writes:
> 
>> The recently introduced -async-teardown commandline option was not
>> wired up properly and did not show up in the output of the QMP command
>> query-command-line-options. This means that libvirt will have no way to
>> discover whether the feature is supported.
> 
> There was nothing improper in its wiring.  The issue is that
> query-command-line-options is junk.  See my recent post
> 
>      Subject: query-command-line-options (was: [PATCH 1/7] qemu: capabilities: Introduce QEMU_CAPS_MACHINE_ACPI)
>      Date: Tue, 07 Mar 2023 10:40:23 +0100
>      Message-ID: <87jzzsc320.fsf_-_@pond.sub.org>
> 
>> This patch fixes the issue by correctly wiring up the commandline
>> option so that it appears in the output of query-command-line-options.
>>
>> Reported-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
>> Fixes: c891c24b1a ("os-posix: asynchronous teardown for shutdown on Linux")
>> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
>> ---
>>   util/async-teardown.c | 17 +++++++++++++++++
>>   1 file changed, 17 insertions(+)
>>
>> diff --git a/util/async-teardown.c b/util/async-teardown.c
>> index 62cdeb0f20..c9b9a3cdb2 100644
>> --- a/util/async-teardown.c
>> +++ b/util/async-teardown.c
>> @@ -12,6 +12,9 @@
>>    */
>>   
>>   #include "qemu/osdep.h"
>> +#include "qemu/config-file.h"
>> +#include "qemu/option.h"
>> +#include "qemu/module.h"
>>   #include <dirent.h>
>>   #include <sys/prctl.h>
>>   #include <sched.h>
>> @@ -144,3 +147,17 @@ void init_async_teardown(void)
>>       clone(async_teardown_fn, new_stack_for_clone(), CLONE_VM, NULL);
>>       sigprocmask(SIG_SETMASK, &old_signals, NULL);
>>   }
>> +
>> +static QemuOptsList qemu_async_teardown_opts = {
>> +    .name = "async-teardown",
>> +    .head = QTAILQ_HEAD_INITIALIZER(qemu_async_teardown_opts.head),
>> +    .desc = {
>> +        { /* end of list */ }
>> +    },
>> +};
>> +
>> +static void register_async_teardown(void)
>> +{
>> +    qemu_add_opts(&qemu_async_teardown_opts);
>> +}
>> +opts_init(register_async_teardown);
> 
> Now it *is* improperly wired up :)
> 
> You're defining new QemuOpts config group "async-teardown" with
> arbitrary option parameters, but don't actually use it for parsing or
> recording the option.  I figure because you can't: there is no option
> argument to parse and record, which is what QemuOpts is designed to do.
> 
> If you need the feature to be visible in query-command-line-options, you
> should make it an option parameter (a KEY, not a GROUP), preferably of
> an existing group / option.

Would it make sense to add it e.g. to "-action" instead, i.e. something like 
"-action teardown=async" ?

  Thomas