Re: [Qemu-devel] Crash with pcie-pci-bridge on qemu-system-s390x

[Aleksandr Bezzubikov]

2017-11-02 17:42 GMT+03:00 Marcel Apfelbaum <address@hidden>:
> On 02/11/2017 16:19, Thomas Huth wrote:
>>
>>   Hi,
>>
>
> Hi Thomas,
>

Hi Thomas, Marcel,

>> seems like there's a new way to crash QEMU with the pcie-pci-bridge
>> device (using QEMU master branch of today):
>>  > $ s390x-softmmu/qemu-system-s390x -nographic -S
>> QEMU 2.10.50 monitor - type 'help' for more information
>> (qemu) device_add pcie-pci-bridge,id=x
>> Segmentation fault (core dumped)
>>
>
> Thanks for noticing it.
>
>> Does anybody have a clue what might be wrong here?
>>
>
> It was tested with X86 and I think aarch64.
> I am not sure how it would work with or if we
> really need it for s390.
>
> We need the device to start a PCI hierarchy by plugging
> it to PCIe Root Port. If I understand correctly s390
> does not use PCIe Root Ports and may not need it.
>

Personally I can see 2 issues here:
1) [Marcel's already mentioned it] It seems that s390x machines have
only pure PCI hosts,
that's why it's a bit weird to put pcie-pci-bridge into the host
2) The actual segfault cause is bridge parent bus not having a parent
device (somehow).
Maybe it's a consequence of point 1)

> If the assumption is correct I suppose we should only
> be compiled into the above archs.
> If you agree, I can post a patch for this.
>
> Thanks,
> Marcel
>
>
>> Backtrace looks like this:
>>
>> #0  0x000055555577064b in pci_default_write_config (address@hidden,
>> address@hidden, val_in=1, address@hidden) at
>> /home/thuth/devel/qemu/hw/pci/pci.c:1367
>> #1  0x00005555556c885f in s390_pcihost_hot_plug (hotplug_dev=<optimized
>> out>, dev=0x55555639b160, errp=0x7fffffffc5a0) at
>> /home/thuth/devel/qemu/hw/s390x/s390-pci-bus.c:684
>> #2  0x000055555575afeb in device_set_realized (obj=<optimized out>,
>> value=<optimized out>, errp=0x7fffffffc6d8) at
>> /home/thuth/devel/qemu/hw/core/qdev.c:936
>> #3  0x00005555557ee48e in property_set_bool (obj=0x55555639b160,
>> v=<optimized out>, name=<optimized out>, opaque=0x555556399fe0,
>> errp=0x7fffffffc6d8)
>>      at /home/thuth/devel/qemu/qom/object.c:1906
>> #4  0x00005555557f25ff in object_property_set_qobject
>> (address@hidden, address@hidden,
>> address@hidden "realized",
>> address@hidden) at
>> /home/thuth/devel/qemu/qom/qom-qobject.c:27
>> #5  0x00005555557f0270 in object_property_set_bool (obj=0x55555639b160,
>> value=<optimized out>, name=0x5555559a4157 "realized",
>> errp=0x7fffffffc6d8)
>>      at /home/thuth/devel/qemu/qom/object.c:1171
>> #6  0x000055555570b549 in qdev_device_add
>> (address@hidden, address@hidden) at
>> /home/thuth/devel/qemu/qdev-monitor.c:632
>> ...
>>
>>   Thomas
>>
>

Thanks,
Aleksandr Bezzubikov