Re: [Qemu-devel] [PULL v2 01/28] hw: apply accel compat properties without touching globals

[Peter Maydell]

On Mon, 7 Jan 2019 at 12:23, Marc-André Lureau
<address@hidden> wrote:
>
> Instead of registering compat properties as globals, let's keep them
> in their own array, to avoid mixing with user globals.
>
> Introduce object_apply_global_props() function, to apply compatibility
> properties from a GPtrArray.

> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 6b3cc55b27..53b507164f 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -972,6 +972,15 @@ static void device_initfn(Object *obj)
>
>  static void device_post_init(Object *obj)
>  {
> +    if (object_dynamic_cast(qdev_get_machine(), TYPE_MACHINE)) {
> +        MachineState *m = MACHINE(qdev_get_machine());
> +        AccelClass *ac = ACCEL_GET_CLASS(m->accelerator);
> +
> +        if (ac->compat_props) {
> +            object_apply_global_props(obj, ac->compat_props, &error_abort);
> +        }
> +    }
> +
>      qdev_prop_set_globals(DEVICE(obj));
>  }


Hi; I've just noticed that this commit seems to break
"-device whatever,help" :

$ gdb --args ./build/x86/arm-softmmu/qemu-system-arm -device iotkit,help -M virt
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1
[...]
(gdb) r
Starting program:
/home/petmay01/linaro/qemu-from-laptop/qemu/build/x86/arm-softmmu/qemu-system-arm
-device iotkit,help -M virt
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffce6c1700 (LWP 23277)]

Thread 1 "qemu-system-arm" received signal SIGSEGV, Segmentation fault.
0x0000555555d985d1 in object_get_class (obj=0x0)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:857
857         return obj->class;
(gdb) bt
#0  0x0000555555d985d1 in object_get_class (obj=0x0)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:857
#1  0x0000555555b5675d in object_apply_compat_props (obj=0x555556b42600)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/hw/core/qdev.c:978
#2  0x0000555555b567f0 in device_post_init (obj=0x555556b42600)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/hw/core/qdev.c:989
#3  0x0000555555d97294 in object_post_init_with_type
(obj=0x555556b42600, ti=0x5555569f7840)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:365
#4  0x0000555555d972c2 in object_post_init_with_type
(obj=0x555556b42600, ti=0x5555569f8640)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:369
#5  0x0000555555d972c2 in object_post_init_with_type
(obj=0x555556b42600, ti=0x555556a12c60)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:369
#6  0x0000555555d97572 in object_initialize_with_type
(data=0x555556b42600, size=1056, type=0x555556a12c60) at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:425
#7  0x0000555555d975b0 in object_initialize (data=0x555556b42600,
size=1056, typename=0x555555ff3ee1 "armv7m_systick") at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:432
#8  0x0000555555d976fd in object_initialize_childv
(parentobj=0x555556b40fa0, propname=0x555555ff3f36 "systick-reg-ns",
childobj=0x555556b42600, size=1056, type=0x555555ff3ee1
"armv7m_systick", errp=0x5555569775f8 <error_abort>,
vargs=0x7fffffffd7c0)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:455
#9  0x0000555555d97689 in object_initialize_child
(parentobj=0x555556b40fa0, propname=0x555555ff3f36 "systick-reg-ns",
childobj=0x555556b42600, size=1056, type=0x555555ff3ee1
"armv7m_systick", errp=0x5555569775f8 <error_abort>) at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:442
#10 0x0000555555b5d049 in sysbus_init_child_obj
(parent=0x555556b40fa0, childname=0x555555ff3f36 "systick-reg-ns",
child=0x555556b42600, childsize=1056, childtype=0x555555ff3ee1
"armv7m_systick")
    at /home/petmay01/linaro/qemu-from-laptop/qemu/hw/core/sysbus.c:376
#11 0x00005555559231b0 in armv7m_nvic_instance_init (obj=0x555556b40fa0)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/hw/intc/armv7m_nvic.c:2393
#12 0x0000555555d97263 in object_init_with_type (obj=0x555556b40fa0,
ti=0x5555569cbce0)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:358
#13 0x0000555555d9755f in object_initialize_with_type
(data=0x555556b40fa0, size=7840, type=0x5555569cbce0) at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:424
#14 0x0000555555d975b0 in object_initialize (data=0x555556b40fa0,
size=7840, typename=0x555556019af8 "armv7m_nvic") at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:432
#15 0x0000555555d976fd in object_initialize_childv
(parentobj=0x555556b40c90, propname=0x555556019b04 "nvnic",
childobj=0x555556b40fa0, size=7840, type=0x555556019af8 "armv7m_nvic",
errp=0x5555569775f8 <error_abort>, vargs=0x7fffffffda90)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:455
#16 0x0000555555d97689 in object_initialize_child
(parentobj=0x555556b40c90, propname=0x555556019b04 "nvnic",
childobj=0x555556b40fa0, size=7840, type=0x555556019af8 "armv7m_nvic",
errp=0x5555569775f8 <error_abort>) at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:442
#17 0x0000555555b5d049 in sysbus_init_child_obj
(parent=0x555556b40c90, childname=0x555556019b04 "nvnic",
child=0x555556b40fa0, childsize=7840, childtype=0x555556019af8
"armv7m_nvic")
    at /home/petmay01/linaro/qemu-from-laptop/qemu/hw/core/sysbus.c:376
#18 0x00005555559c63ba in armv7m_instance_init (obj=0x555556b40c90)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/hw/arm/armv7m.c:137
#19 0x0000555555d97263 in object_init_with_type (obj=0x555556b40c90,
ti=0x5555569db4c0)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:358
#20 0x0000555555d9755f in object_initialize_with_type
(data=0x555556b40c90, size=11152, type=0x5555569db4c0) at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:424
#21 0x0000555555d975b0 in object_initialize (data=0x555556b40c90,
size=11152, typename=0x555556022fd1 "armv7m") at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:432
#22 0x0000555555d976fd in object_initialize_childv
(parentobj=0x555556b40980, propname=0x555556022fd1 "armv7m",
childobj=0x555556b40c90, size=11152, type=0x555556022fd1 "armv7m",
errp=0x5555569775f8 <error_abort>, vargs=0x7fffffffdd50)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:455
#23 0x0000555555d97689 in object_initialize_child
(parentobj=0x555556b40980, propname=0x555556022fd1 "armv7m",
childobj=0x555556b40c90, size=11152, type=0x555556022fd1 "armv7m",
errp=0x5555569775f8 <error_abort>) at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:442
#24 0x0000555555b5d049 in sysbus_init_child_obj
(parent=0x555556b40980, childname=0x555556022fd1 "armv7m",
child=0x555556b40c90, childsize=11152, childtype=0x555556022fd1
"armv7m")
    at /home/petmay01/linaro/qemu-from-laptop/qemu/hw/core/sysbus.c:376
#25 0x00005555559f3fdc in iotkit_init (obj=0x555556b40980)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/hw/arm/iotkit.c:115
#26 0x0000555555d97263 in object_init_with_type (obj=0x555556b40980,
ti=0x5555569df840)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:358
#27 0x0000555555d9755f in object_initialize_with_type
(data=0x555556b40980, size=50080, type=0x5555569df840) at
/home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:424
#28 0x0000555555d97bb9 in object_new_with_type (type=0x5555569df840)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:588
#29 0x0000555555d97bf6 in object_new (typename=0x555556a2b230 "iotkit")
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qom/object.c:598
#30 0x0000555555aafe8c in qmp_device_list_properties
(typename=0x555556a2b230 "iotkit", errp=0x7fffffffe050) at
/home/petmay01/linaro/qemu-from-laptop/qemu/qmp.c:519
#31 0x0000555555a8607a in qdev_device_help (opts=0x555556a2b1c0)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/qdev-monitor.c:283
#32 0x0000555555a8f77e in device_help_func (opaque=0x0,
opts=0x555556a2b1c0, errp=0x0)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/vl.c:2299
#33 0x0000555555ef5b21 in qemu_opts_foreach (list=0x555556787040
<qemu_device_opts>, func=0x555555a8f75e <device_help_func>,
opaque=0x0, errp=0x0)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/util/qemu-option.c:1171
#34 0x0000555555a94310 in main (argc=5, argv=0x7fffffffe408,
envp=0x7fffffffe438)
    at /home/petmay01/linaro/qemu-from-laptop/qemu/vl.c:4323

Looking at the backtrace, this seems to happen because in
device_post_init we look at m->accelerator, but m->accelerator
is only set when vl.c calls configure_accelerator(), so if
this function gets called before then, it will cause an assert.
In particular, the handling of -device foo,help happens before the
accelerator is configured. (Possibly other things may cause
device init before then too?)

thanks
-- PMM