Re: [PATCH v4 1/2] xen/passthrough: Provide stub functions when !HAS_PASSTHROUGH

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

Hi Jan,

>>>> +
>>>> +static inline int iommu_domain_init(struct domain *d, unsigned int opts)
>>>> +{
>>>> +    /*
>>>> +     * Return as the real iommu_domain_init() would: Success when
>>>> +     * !is_iommu_enabled(), following from !iommu_enabled when 
>>>> !HAS_PASSTHROUGH
>>>> +     */
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static inline void iommu_hwdom_init(struct domain *d) {}
>>>> +
>>>> +static inline void iommu_domain_destroy(struct domain *d) {}
>>>> +
>>>> +#endif /* HAS_PASSTHROUGH */
>>>> +
>>>> /*
>>>>  * The following flags are passed to map (applicable ones also to unmap)
>>>>  * operations, while some are passed back by lookup operations.
>>>> @@ -209,6 +233,8 @@ struct msi_msg;
>>>> #ifdef CONFIG_HAS_DEVICE_TREE
>>>> #include <xen/device_tree.h>
>>>> +#ifdef CONFIG_HAS_PASSTHROUGH
>>>> +
>>>> int iommu_assign_dt_device(struct domain *d, struct dt_device_node *dev);
>>>> int iommu_deassign_dt_device(struct domain *d, struct dt_device_node *dev);
>>>> int iommu_dt_domain_init(struct domain *d);
>>>> @@ -238,6 +264,26 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, 
>>>> struct domain *d,
>>>>  */
>>>> int iommu_remove_dt_device(struct dt_device_node *np);
>>>> +#else
>>>> +
>>>> +static inline int iommu_assign_dt_device(struct domain *d,
>>>> +                                         struct dt_device_node *dev)
>>>> +{
>>>> +    return -EINVAL;
>>>> +}
>>>> +
>>>> +static inline int iommu_add_dt_device(struct dt_device_node *np)
>>>> +{
>>>> +    return 1;
>>> 
>>> I would suggest to add a comment explain what 1 means. IIRC, this means "no 
>>> iommu" present.
>> 
>> Would it be ok something like in iommu_domain_init:
>> 
>> /*
>> * Returns as the real iommu_add_dt_device() would: Error “no iommu" because
>> * !iommu_enabled due to the fact that !HAS_PASSTHROUGH
>> */
> 
> We had been there before, hadn't we? Personally I find the suggested text
> hard to follow.

well, I’ve taken your suggestion for iommu_domain_init and adapted here, 
maybe the adaptation didn’t meet your criteria then :)

But ...

> How about
> 
>    /*
>     * !HAS_PASSTHROUGH => !iommu_enabled (see the non-stub
>     * iommu_add_dt_device())
>     */
> 
> If that's too terse, adding a few words should be fine.

as long as you are happy with that, I’m happy as well, please let me know
if you want a v5 with this or if you would do the modificaiton on commit.

Cheers,
Luca