On 4 September 2017 at 20:38, Igor Mammedov <imamm...@redhat.com> wrote: > On Mon, 4 Sep 2017 17:36:59 +0100 > Peter Maydell <peter.mayd...@linaro.org> wrote: > >> I just got bitten by qdev_get_machine()'s behaviour on the user-only >> emulators, where it can return something that isn't NULL and isn't >> an instance of TYPE_MACHINE either. > user-only shouldn't get to qdev_get_machine() at all, > issue probably in container_get().
I need it in cpu_common_realizefn(), for http://patchwork.ozlabs.org/patch/797940/ > I'd try to fix wrong user if possible and maybe add ifdef build failure > to qdev_get_machine() so it would not build in user mode. Can't ifdef, that source file is built once for all targets. My fix (which I intend to send to the list today) is to make it do the object_dynamic_cast() check -- if that doesn't give a TYPE_MACHINE then we're in user mode and don't need to set ignore_memory_transaction_failures on the cpu object anyway. >> It looks like maybe this can happen in some cases in softmmu too, >> judging by the way that qdev_get_hotplug_handler() does an >> object_dynamic_cast() check that it really got back a TYPE_MACHINE. > As I recall only bus or machine provide hotplug_handler currently, > but it's possible to extend to other objects if we find use-case. > > We could do static cast to machine instead dynamic there but > in hotplug case it will abort QEMU if error happens, > hence dynamic check to avoid be more resilient during hotplug. > (well, if qdev_get_machine() returns not machine during startup > we would be screwed anyways, but that should break much earlier) If this can't ever happen then we should be aborting; that's the idea behind the cast macros doing assertions. I'm not sure hotplug needs to be special here if it doesn't have a genuine reason to think it might get back something of the wrong type. thanks -- PMM
