Re: [RFC 3/3] qom: Improve error message in module_object_class_by_name()

["Jose R. Ziviani" <jziviani@suse.de>]

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On Mon, Jul 19, 2021 at 05:29:49PM +0200, Claudio Fontana wrote:
> On 7/1/21 1:27 AM, Jose R. Ziviani wrote:
> > module_object_class_by_name() calls module_load_qom_one if the object
> > is provided by a dynamically linked library. Such library might not be
> > available at this moment - for instance, it can be a package not yet
> > installed. Thus, instead of assert error messages, this patch outputs
> > more friendly messages.
> > 
> > Current error messages:
> > $ ./qemu-system-x86_64 -machine q35 -accel tcg -kernel /boot/vmlinuz
> > ...
> > ERROR:../accel/accel-softmmu.c:82:accel_init_ops_interfaces: assertion failed: (ops != NULL)
> > Bail out! ERROR:../accel/accel-softmmu.c:82:accel_init_ops_interfaces: assertion failed: (ops != NULL)
> > [1]    31964 IOT instruction (core dumped)  ./qemu-system-x86_64 ...
> > 
> > New error message:
> > $ ./qemu-system-x86_64 -machine q35 -accel tcg -kernel /boot/vmlinuz
> > accel-tcg-x86_64 module is missing, install the package or config the library path correctly.
> > 
> > $ make check
> > ...
> > Running test qtest-x86_64/test-filter-mirror
> > Running test qtest-x86_64/endianness-test
> > accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
> > accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
> > accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
> > accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
> > accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
> > accel-tcg-x86_64 module is missing, install the package or config the library path correctly.
> > ...
> > 
> > Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
> > ---
> >  qom/object.c | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> > 
> > diff --git a/qom/object.c b/qom/object.c
> > index 6a01d56546..2d40245af9 100644
> > --- a/qom/object.c
> > +++ b/qom/object.c
> > @@ -1024,6 +1024,24 @@ ObjectClass *object_class_by_name(const char *typename)
> >      return type->class;
> >  }
> >  
> > +char *get_accel_module_name(const char *ac_name);
> > +
> > +char *get_accel_module_name(const char *ac_name)
> > +{
> > +    size_t len = strlen(ac_name);
> > +    char *module_name = NULL;
> > +
> > +    if (strncmp(ac_name, "tcg-accel-ops", len) == 0) {
> > +#ifdef CONFIG_TCG_MODULAR
> > +        module_name = g_strdup_printf("%s%s", "accel-tcg-", "x86_64");
> > +#endif
> > +    } else if (strncmp(ac_name, "qtest-accel-ops", len) == 0) {
> > +        module_name = g_strdup_printf("%s%s", "accel-qtest-", "x86_64");
> > +    }
> > +
> > +    return module_name;
> > +}
> > +
> >  ObjectClass *module_object_class_by_name(const char *typename)
> >  {
> >      ObjectClass *oc;
> > @@ -1031,8 +1049,20 @@ ObjectClass *module_object_class_by_name(const char *typename)
> >      oc = object_class_by_name(typename);
> >  #ifdef CONFIG_MODULES
> >      if (!oc) {
> > +        char *module_name;
> >          module_load_qom_one(typename);
> >          oc = object_class_by_name(typename);
> > +        module_name = get_accel_module_name(typename);
> > +        if (module_name) {
> > +            if (!module_is_loaded(module_name)) {
> > +                fprintf(stderr, "%s module is missing, install the "
> > +                                "package or config the library path "
> > +                                "correctly.\n", module_name);
> > +                g_free(module_name);
> > +                exit(1);
> > +            }
> > +            g_free(module_name);
> > +        }
> >      }
> >  #endif
> >      return oc;
> > 
> 
> Hi Jose,
> 
> this inserts accel logic into module_object_class_by_name,
> maybe some other place would be better to insert this check,
> like when trying to select an accelerator?


Hello Claudio,

Yes, I think that 'get_accel_module_name()' may be a more generic
'get_module_name()' to handle any module failure (not only
accelerators).

I'll improve it and send a v2. Thank you for reviewing it.

> 
> Thanks,
> 
> CLaudio

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