Peter Xu <pet...@redhat.com> writes:
> X86 IOMMUs cannot be created more than one on a system yet. Make it a
> singleton so it guards the system from accidentally create yet another
> IOMMU object when one already presents.
>
> Now if someone tries to create more than one, e.g., via:
>
> ./qemu -M q35 -device intel-iommu -device intel-iommu
>
> The error will change from:
>
> qemu-system-x86_64: -device intel-iommu: QEMU does not support multiple
> vIOMMUs for x86 yet.
>
> To:
>
> qemu-system-x86_64: -device intel-iommu: Class 'intel-iommu' only supports
> one instance
>
> Unfortunately, yet we can't remove the singleton check in the machine
> hook (pc_machine_device_pre_plug_cb), because there can also be
> virtio-iommu involved, which doesn't share a common parent class yet.
>
> But with this, it should be closer to reach that goal to check singleton by
> QOM one day.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
$ qemu-system-x86_64 -device amd-iommu,help
/work/armbru/qemu/include/hw/boards.h:24:MACHINE: Object 0x56473906f960 is not
an instance of type machine
Aborted (core dumped)
(gdb) bt
#0 0x00007ffff4e43834 in __pthread_kill_implementation () at /lib64/libc.so.6
#1 0x00007ffff4df18ee in raise () at /lib64/libc.so.6
#2 0x00007ffff4dd98ff in abort () at /lib64/libc.so.6
#3 0x0000555555f75ef3 in object_dynamic_cast_assert
(obj=0x555557e03960, typename=0x5555563c403e "machine", file=0x5555563c4018
"/work/armbru/qemu/include/hw/boards.h", line=24, func=0x5555563c4290
<__func__.7> "MACHINE") at ../qom/object.c:936
#4 0x0000555555d5db0f in MACHINE (obj=0x555557e03960)
at /work/armbru/qemu/include/hw/boards.h:24
#5 0x0000555555d5e030 in x86_iommu_get_default () at ../hw/i386/x86-iommu.c:83
#6 0x0000555555d5e262 in x86_iommu_get_instance
(errp=0x5555573d4918 <error_abort>) at ../hw/i386/x86-iommu.c:139
#7 0x0000555555f7c27c in singleton_get_instance (class=0x555557e00320)
at ../qom/object_interfaces.c:371
#8 0x000055555612a842 in qmp_device_list_properties
(typename=0x555557e001d0 "amd-iommu", errp=0x7fffffffda38)
at ../qom/qom-qmp-cmds.c:147
#9 0x0000555555bf20b2 in qdev_device_help (opts=0x555557e001f0)
at ../system/qdev-monitor.c:314
#10 0x0000555555bfe06d in device_help_func
(opaque=0x0, opts=0x555557e001f0, errp=0x0) at ../system/vl.c:1208
#11 0x0000555556217186 in qemu_opts_foreach
(list=0x55555729e5c0 <qemu_device_opts>, func=0x555555bfe04d
<device_help_func>, opaque=0x0, errp=0x0) at ../util/qemu-option.c:1135
#12 0x0000555555c01d56 in qemu_process_help_options () at ../system/vl.c:2555
#13 0x0000555555c04d81 in qemu_init (argc=3, argv=0x7fffffffde28)
at ../system/vl.c:3654
#14 0x000055555612ffae in main (argc=3, argv=0x7fffffffde28)
at ../system/main.c:47
