Peter Maydell <peter.mayd...@linaro.org> writes:
> On Fri, 13 Sept 2024 at 11:02, Markus Armbruster <arm...@redhat.com> wrote:
>>
>> Fabiano Rosas <faro...@suse.de> writes:
>> > I could add error/warn variants that are noop in case qtest is
>> > enabled. It would, however, lead to this pattern which is discouraged by
>> > the error.h documentation (+Cc Markus for advice):
>> >
>> > before:
>> > if (!dinfo && !qtest_enabled()) {
>> > error_report("A flash image must be given with the "
>> > "'pflash' parameter");
>> > exit(1);
>> > }
>>
>> This is connex_init() and verdex_init() in hw/arm/gumstix.c.
>>
>> qtest_enabled() is *not* just suppressing a warning here, it's
>> suppressing a fatal error. We use it to take a different codepath,
>> which is what Peter called out as a bad idea.
>>
>> Comes from commit bdf921d65f8 (gumstix: Don't enforce use of -pflash for
>> qtest).
>
> The good news on this one is that gumstix.c goes away in the
> "arm: Drop deprecated boards" series, so this specific
> error is moot :-) But it's in the same category as various
> "-kernel is mandatory except with qtest" machine checks.
>
>> > after:
>> > if (!dinfo) {
>> > error_report_noqtest(&error_fatal,
>> > "A flash image must be given with the "
>> > "'pflash' parameter");
>> > }
>>
>> I don't like creating infrastructure to make bad ideas look less
>> obviously bad.
>>
>> > For both error/warn, we'd reduce the amount of qtest_enabled() to only
>> > the special cases not related to printing. We'd remove ~35/83 instances,
>> > not counting the 7 printfs.
>> >
>> >> Some categories as a starter:
>> >> * some board models will error-and-exit if the user
>> >> didn't provide any guest code (eg no -kernel option),
>> >> like hw/m68k/an5206.c. When we're running with the
>> >> qtest accelerator it's fine and expected that there's
>> >> no guest code loaded because we'll never run any guest code
>>
>> Having tests provide the things users need to provide feels better. It
>> may not always be practical.
>
> Specifically, if you don't disable the error-exit when qtest
> is in use, then the generic qom-test tests which say "can we
> at least instantiate every machine?" will fail, because they
> assume that "qemu-system-foo -machine bar -accel qtest" will
> at least start.
>
> It doesn't really seem feasible to me to have qom-test
> know about every machine's specific requirements for
> how to pass a guest image.
Yes.
> The other approach would be to standardize on "every machine
> type should happily start up with no warnings even if there
> is no guest code specified by the user and it would simply
> execute zeroes". We already do this for quite a lot of
> boards, including some major ones, so we're certainly not
> consistent about trying to diagnose user errors in this area.
Fatal error unless qtest is bad, because we take a different path.
Silently executing zero can be hard for users to diagnose.
Possible compromise: warn unless qtest?
