Re: [Qemu-devel] [PATCH 1/8] machine: query iommu machine property rather than qemu opts

[Marcel Apfelbaum <marcel@redhat.com>]

On 02/04/2015 06:47 PM, Markus Armbruster wrote:
> Marcel Apfelbaum <marcel@redhat.com> writes:
>
>> Fixes a QEMU crash when passing iommu parameter in command line.
>>
>> Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
>> ---
>>   hw/core/machine.c   | 5 +++++
>>   hw/pci-host/q35.c   | 2 +-
>>   include/hw/boards.h | 1 +
>>   3 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/core/machine.c b/hw/core/machine.c
>> index fbd91be..096eb10 100644
>> --- a/hw/core/machine.c
>> +++ b/hw/core/machine.c
>> @@ -403,6 +403,11 @@ bool machine_usb(MachineState *machine)
>>       return machine->usb;
>>   }
>>
>> +bool machine_iommu(MachineState *machine)
>> +{
>> +    return machine->iommu;
>> +}
>> +
>>   static const TypeInfo machine_info = {
>>       .name = TYPE_MACHINE,
>>       .parent = TYPE_OBJECT,
>
> What does this buy us over a straight current_machine->iommu?
Following QOM guidelines/conventions all object fields are private
to machine files only. The *only* ways that they can be exposed are:
1. A wrapper
2. object_property_get...

I chose the wrapper because the other variant would be really
ugly and should be used only on a generic code.

This is the real reason I used this, but pure theoretical speaking
using  wrappers will give us the opportunity to change machine_iommu
implementation without the need to change the call sites.

To wrap it up, I just followed previous comments I received on QOM handling.

Thanks,
Marcel

>
> Same for the other wrapper functions.
>
> [...]
>