Re: [PATCH v16 03/99] qtest: Add qtest_has_accel() method

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 6/7/21 3:16 PM, Thomas Huth wrote:
> On 04/06/2021 17.51, Alex Bennée wrote:
>> From: Philippe Mathieu-Daudé <philmd@redhat.com>
>>
>> Introduce the qtest_has_accel() method which allows a runtime
>> query on whether a QEMU instance has an accelerator built-in.
>>
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Message-Id: <20210505125806.1263441-4-philmd@redhat.com>
>> ---
>>   tests/qtest/libqos/libqtest.h |  8 ++++++++
>>   tests/qtest/libqtest.c        | 29 +++++++++++++++++++++++++++++
>>   2 files changed, 37 insertions(+)

>>   +bool qtest_has_accel(const char *accel_name)
>> +{
>> +    bool has_accel = false;
>> +    QDict *response;
>> +    QList *accels;
>> +    QListEntry *accel;
>> +    QTestState *qts;
>> +
>> +    qts = qtest_initf("-accel qtest -machine none");
>> +    response = qtest_qmp(qts, "{'execute': 'query-accels'}");
>> +    accels = qdict_get_qlist(response, "return");
>> +
>> +    QLIST_FOREACH_ENTRY(accels, accel) {
>> +        QDict *accel_dict = qobject_to(QDict, qlist_entry_obj(accel));
>> +        const char *name = qdict_get_str(accel_dict, "name");
>> +
>> +        if (g_str_equal(name, accel_name)) {
>> +            has_accel = true;
>> +            break;
>> +        }
>> +    }
>> +    qobject_unref(response);
>> +
>> +    qtest_quit(qts);
>> +
>> +    return has_accel;
>> +}
> 
> This spawns a new instance of QEMU each time the function is called -
> which could slow down testing quite a bit if a test calls this function
> quite often. Would it be feasible to cache this information, so that you
> only have to run a new instance of QEMU once?

Good idea!