Re: [Qemu-devel] [PATCH 5/7] qdev: Protect device-list-properties against broken devices

[Thomas Huth <thuth@redhat.com>]

On 21/09/15 18:39, Markus Armbruster wrote:
> Thomas Huth <thuth@redhat.com> writes:
> 
>> On 21/09/15 08:14, Markus Armbruster wrote:
>>> Eduardo Habkost <ehabkost@redhat.com> writes:
>>>
>>>> On Fri, Sep 18, 2015 at 08:42:54PM +0200, Thomas Huth wrote:
>>>>> On 18/09/15 14:00, Markus Armbruster wrote:
>>>>>> Several devices don't survive object_unref(object_new(T)): they crash
>>>>>> or hang during cleanup, or they leave dangling pointers behind.
>>>>>>
>>>>>> This breaks at least device-list-properties, because
>>>>>> qmp_device_list_properties() needs to create a device to find its
>>>>>> properties.  Broken in commit f4eb32b "qmp: show QOM properties in
>>>>>> device-list-properties", v2.1.  Example reproducer:
>>>>>>
>>>>>>     $ qemu-system-aarch64 -nodefaults -display none -machine none -S -qmp stdio
>>>>>>     {"QMP": {"version": {"qemu": {"micro": 50, "minor": 4, "major": 2}, "package": ""}, "capabilities": []}}
>>>>>>     { "execute": "qmp_capabilities" }
>>>>>>     {"return": {}}
>>>>>>     { "execute": "device-list-properties", "arguments": { "typename": "pxa2xx-pcmcia" } }
>>>>>>     qemu-system-aarch64: /home/armbru/work/qemu/memory.c:1307: memory_region_finalize: Assertion `((&mr->subregions)->tqh_first == ((void *)0))' failed.
>>>>>>     Aborted (core dumped)
>>>>>>     [Exit 134 (SIGABRT)]
>>>>>>
>>>>>> Unfortunately, I can't fix the problems in these devices right now.
>>>>>> Instead, add DeviceClass member cannot_even_create_with_object_new_yet
>>>>>> to mark them:
>>>>>>
>>>>>> * Crash or hang during cleanup (didn't debug them, so I can't say
>>>>>>   why): "pxa2xx-pcmcia", "realview_pci", "versatile_pci",
>>>>>>   "s390-sclp-event-facility", "sclp"
>>>>>>
>>>>>> * Dangling pointers: all CPUs, plus "allwinner-a10", "digic",
>>>>>>   "fsl,imx25", "fsl,imx31", "xlnx,zynqmp", because they create CPUs
>>>>>>
>>>>>> * Assert kvm_enabled(): "host-x86_64-cpu", host-i386-cpu",
>>>>>>   "host-powerpc64-cpu", "host-embedded-powerpc-cpu",
>>>>>>   "host-powerpc-cpu"
>>>>>
>>>>> I just had a look at the powerpc code - you're likely talking about
>>>>> the "assert(kvm_enabled());" in the kvmppc_host_cpu_initfn() in
>>>>> target-ppc/kvm.c ? That should be fine, I think, because
>>>>> kvm_ppc_register_host_cpu_type() is only done on ppc when KVM has been
>>>>> enabled.
>>>
>>> Easy to verify on a KVM-capable PPC host: try -device C,help with KVM on
>>> and off, where C is the appropriate host CPU.
>>
>> In both cases (KVM on and off), I simply get:
>>
>> # qemu-system-ppc64 -machine accel=tcg -device host-powerpc64-cpu,help
>> 'host-powerpc64-cpu' is not a valid device model name
>> # qemu-system-ppc64 -machine accel=kvm -device host-powerpc64-cpu,help
>> 'host-powerpc64-cpu' is not a valid device model name
>>
>> No crash/abort here.
> 
> No introspection, either.  Can you try the same with QMP command
> device-list-properties?

# ppc64-softmmu/qemu-system-ppc64 -nodefaults -S -display none -qmp stdio
{"QMP": {"version": {"qemu": {"micro": 50, "minor": 4, "major": 2}, "package": ""}, "capabilities": []}}
{ "execute": "qmp_capabilities" }
{"return": {}}
{ "execute": "device-list-properties", "arguments": { "typename": "host-powerpc64-cpu" } }
{"error": {"class": "DeviceNotFound", "desc": "Device 'host-powerpc64-cpu' not found"}}
{ "execute": "quit" }
{"return": {}}
{"timestamp": {"seconds": 1442856053, "microseconds": 732079}, "event": "SHUTDOWN"}

# ppc64-softmmu/qemu-system-ppc64 -machine accel=kvm -nodefaults -S -display none -qmp stdio
{"QMP": {"version": {"qemu": {"micro": 50, "minor": 4, "major": 2}, "package": ""}, "capabilities": []}}
{ "execute": "qmp_capabilities" }
{"return": {}}
{ "execute": "device-list-properties", "arguments": { "typename": "host-powerpc64-cpu" } }
{"return": [{"name": "compat", "description": "compatibility mode, power6/power7/power8", "type": "str"}]}
{ "execute": "quit" }
{"return": {}}
{"timestamp": {"seconds": 1442856113, "microseconds": 913588}, "event": "SHUTDOWN"}

 Thomas