Re: [Qemu-devel] Running QEMU without default devices / kernel / bios

[Thomas Huth]

On 08.05.2018 07:33, Thomas Huth wrote:
> On 07.05.2018 21:32, Eduardo Habkost wrote:
>> On Mon, May 07, 2018 at 09:13:57PM +0200, Thomas Huth wrote:
>>> On 07.05.2018 20:21, Eduardo Habkost wrote:
>>>> On Mon, May 07, 2018 at 06:50:35PM +0200, Markus Armbruster wrote:
>>>>> Eduardo Habkost <address@hidden> writes:
>>>>>
>>>>>> On Fri, Apr 27, 2018 at 08:31:58AM +0200, Markus Armbruster wrote:
>>>>>>> Eduardo Habkost <address@hidden> 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 <address@hidden> 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
>>>>
>>>> Makes sense to me.  It looks like the only obstacle for
>>>> tests/device-introspect and device-crash-test is the first rule.
>>>> "Guest won't boot" isn't a problem, but "QEMU won't run" is.
>>>>
>>>> The first rule is easily testable, too: running
>>>> "$QEMU -machine $MACHINE -nodefaults" and not having a working
>>>> QMP monitor should be reported as a bug by automated tests.
>>>
>>> You mean with "-accel qtest" or without? With "-accel qtest" we should
>>> pretty soon be fine, after Peter's current PULL request has been merged
>>> (which contains a patch from me for fixing these SD card problems with
>>> ARM machines).
>>> Without "-accel qtest", things are not that easy, unfortunately. Lots of
>>> boards require "-kernel" or "-bios" and refuse to work without. So you
>>> can hardly test "-nodefaults" automatically in the normal tcg mode. (But
>>> maybe all boards should allow to start QEMU in case you've at least also
>>> specified "-S" ? ... in that case we've got plenty of work for
>>> BiteSizeTasks ;-) )
>>
>> Hmm, maybe it's not a bite-sized task after all.  :)
>>
>> Should we do this gradually?
>>
>> * Working with -accel qtest is useful, and sounds like an easier goal;
> 
> We're pretty much there already. Apart from the SD card problem (and the
> xen boards), all machines should work with -nodefaults in qtest mode now.

I forgot to mention that some sparc machines also still have problems.
Patches are available here:

https://lists.gnu.org/archive/html/qemu-devel/2018-04/msg00543.html

and

https://lists.gnu.org/archive/html/qemu-devel/2018-04/msg00546.html

... but they have not been merged yet.

 Thomas