Re: [Qemu-devel] [RFC PATCH] tests/device-introspect: Test devices with all machines, not only with "none"

[Thomas Huth <thuth@redhat.com>]

On 07.05.2018 18:50, Markus Armbruster wrote:
> Eduardo Habkost <ehabkost@redhat.com> writes:
> 
>> On Fri, Apr 27, 2018 at 08:31:58AM +0200, Markus Armbruster wrote:
>>> Eduardo Habkost <ehabkost@redhat.com> writes:
>>>
>>>> On Thu, Apr 26, 2018 at 05:20:25PM +0200, Thomas Huth wrote:
>>>>> On 26.04.2018 13:45, Markus Armbruster wrote:
>>>>>> Thomas Huth <thuth@redhat.com> writes:
>>>>> [...]
>>>>>>> @@ -260,6 +263,26 @@ static void test_abstract_interfaces(void)
>>>>>>>      qtest_end();
>>>>>>>  }
>>>>>>>  
>>>>>>> +static void add_machine_test_case(const char *mname)
>>>>>>> +{
>>>>>>> +    char *path, *args;
>>>>>>> +
>>>>>>> +    /* Ignore blacklisted machines */
>>>>>>> +    if (g_str_equal("xenfv", mname) || g_str_equal("xenpv", mname)) {
>>>>>>> +        return;
>>>>>>> +    }
>>>>>>> +
>>>>>>> +    path = g_strdup_printf("device/introspect/concrete-defaults-%s", mname);
>>>>>>> +    args = g_strdup_printf("-machine %s", mname);
>>>>>>> +    qtest_add_data_func(path, args, test_device_intro_concrete);
>>>>>>
>>>>>> This runs test_device_intro_concrete() with "-machine M" for all machine
>>>>>> types M, in SPEED=slow mode.
>>>>>>
>>>>>>> +    g_free(path);
>>>>>>> +
>>>>>>> +    path = g_strdup_printf("device/introspect/concrete-nodefaults-%s", mname);
>>>>>>> +    args = g_strdup_printf("-nodefaults -machine %s", mname);
>>>>>>> +    qtest_add_data_func(path, args, test_device_intro_concrete);
>>>>>>
>>>>>> This runs test_device_intro_concrete() with "-nodefaults -machine M" for
>>>>>> all machine types M, in SPEED=slow mode.
>>>>>>
>>>>>> Has "without -nodefaults" exposed additional bugs?
>>>>>
>>>>> After testing this with all machines, I had to discover that
>>>>> "-nodefaults" does not work so easily: A lot of the embedded machines
>>>>> (especially the ARM machines) simply refuse to work with "-nodefaults"
>>>>> and exit immediately instead. E.g.:
>>>>>
>>>>> $ arm-softmmu/qemu-system-arm -nodefaults -nographic -M n810,accel=qtest
>>>>> qemu-system-arm: missing SecureDigital device
>>>
>>> These are all bugs.  --nodefaults is supposed to suppress *optional*
>>> devices, not mandatory ones.
>>
>> I'm not sure I understand the requirements.  What exactly is the
>> definition of "mandatory"?
>>
>> A machine created by "qemu-system-x86_64 -machine pc -nodefaults"
>> is useless because it has no any device to boot from.  How is
>> that different from a n810 machine not booting because there's no
>> SD device?
> 
> I propose:
> 
> * Stuff that's required for QEMU to run is not suppressed by -nodefaults
> 
> * Stuff that a real machine has soldered on is also not suppressed
> 
> * Stuff that can be pulled out of a real machine may be suppressed, even
>   when that means the guest won't run
> 
> Does that make some sense?

Makes sense. On a real machine, you could likely also remove the SD card
and load a kernel by other means, e.g. with a JTAG debug connector. So
it makes sense that you could also start the machine in QEMU without SD
card and load a kernel e.g. with the gdb stub instead.

 Thomas