Re: [PATCH v4] xen/iommu: cleanup iommu related domctl handling

[Jan Beulich <jbeulich@suse.com>]

On 20.04.2022 07:57, Juergen Gross wrote:
> --- a/xen/include/xen/iommu.h
> +++ b/xen/include/xen/iommu.h
> @@ -341,8 +341,17 @@ struct domain_iommu {
>  /* Does the IOMMU pagetable need to be kept synchronized with the P2M */
>  #ifdef CONFIG_HAS_PASSTHROUGH
>  #define need_iommu_pt_sync(d)     (dom_iommu(d)->need_sync)
> +
> +int iommu_do_domctl(struct xen_domctl *domctl, struct domain *d,
> +                    XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl);
>  #else
>  #define need_iommu_pt_sync(d)     ({ (void)(d); false; })
> +
> +static inline int iommu_do_domctl(struct xen_domctl *domctl, struct domain *d,
> +                                  XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
> +{
> +    return -ENOSYS;
> +}

As said in reply to Andrew as well as in a number or earlier occasions,
I firmly think that this wants to be -EOPNOTSUPP, not -ENOSYS. Views
here may differ of course, but in the absence of objections I consider
this easy enough to adjust while committing. If, of course, the
approach finds a majority in the first place - as indicated before I
don't view it as very desirable to enumerate all the IOMMU related
domctl-s in the common handler.

FTAOD I can accept x86'es arch_do_domctl() returning -ENOSYS, but only
for the purpose of not altering the pre-existing error code which would
be returned if making it there.

Jan