Re: [PATCH 2/5] iommu / domctl: introduce XEN_DOMCTL_iommu_ctl

[Jan Beulich <jbeulich@xxxxxxxx>]

On 19.10.2020 09:23, Paul Durrant wrote:
>> From: Julien Grall <julien@xxxxxxx>
>> Sent: 16 October 2020 16:47
>>
>> On 05/10/2020 10:49, Paul Durrant wrote:
>>> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
>>> index 791f0a2592..75e855625a 100644
>>> --- a/xen/include/public/domctl.h
>>> +++ b/xen/include/public/domctl.h
>>> @@ -1130,6 +1130,18 @@ struct xen_domctl_vuart_op {
>>>                                    */
>>>   };
>>>
>>> +/*
>>> + * XEN_DOMCTL_iommu_ctl
>>> + *
>>> + * Control of VM IOMMU settings
>>> + */
>>> +
>>> +#define XEN_DOMCTL_IOMMU_INVALID 0
>>
>> I can't find any user of XEN_DOMCTL_IOMMU_INVALID. What's the purpose
>> for it?
>>
> 
> It's just a placeholder. I think it's generally safer that a zero opcode 
> value is invalid.

But does this then need a #define? Starting valid command from 1
ought to be sufficient?

Jan