Re: [PATCH 17/24] XSM: make Argo hooks well-formed ones

[Jan Beulich <jbeulich@suse.com>]

On 04.08.2026 16:27, Jason Andryuk wrote:
> On 2026-08-04 03:53, Jan Beulich wrote:
>> On 03.08.2026 23:01, Jason Andryuk wrote:
>>> On 2026-07-28 09:22, Jan Beulich wrote:
>>>> --- a/xen/include/xsm/dummy.h
>>>> +++ b/xen/include/xsm/dummy.h
>>>
>>>> @@ -751,27 +751,32 @@ static XSM_INLINE int xsm_dm_op(XSM_DEFA
>>>>    #endif
>>>>    
>>>>    #ifdef CONFIG_ARGO
>>>> -static XSM_INLINE int xsm_argo_enable(const struct domain *d)
>>>> +
>>>> +static XSM_INLINE int xsm_argo_enable(XSM_DEFAULT_ARG const struct domain *d)
>>>>    {
>>>> -    return 0;
>>>> +    XSM_ASSERT_ACTION(XSM_HOOK);
>>>> +    return xsm_default_action(action, current->domain, d);
>>>
>>> This one I think should be
>>>       return xsm_default_action(action, d, NULL);
>>>
>>> Usually current is passed in for the check, but for domain_create() ->
>>> argo_init() it is the under-construction domain.
>>
>> And in that case we want to make sure that current->domain may enable Argo
>> for d.
> 
> It's not a hook for current to enable for d, but more of a hook "is d 
> allowed to use argo."
> 
> In the hypercall entry path, it use is clear - "is this domain allowed 
> to make argo hypercalls."
> 
> In argo_init(), it is more of an optimization.  Only initialize if d is 
> allowed to use argo.  I think this use is questionable, but it is the 
> current code.
> 
> In flask, the source is d, the target is xen_t:
>      allow domain_type xen_t:argo enable
> 
> So it is not an operation between domains.
> 
>>>>    }
>>>>    
>>>>    static XSM_INLINE int xsm_argo_register_single_source(
>>>> -    const struct domain *d, const struct domain *t)
>>>> +    XSM_DEFAULT_ARG const struct domain *d, const struct domain *t)
>>>>    {
>>>> -    return 0;
>>>> +    XSM_ASSERT_ACTION(XSM_HOOK);
>>>> +    return xsm_default_action(action, d, t);
>>>>    }
>>>>    
>>>>    static XSM_INLINE int xsm_argo_register_any_source(
>>>> -    const struct domain *d)
>>>> +    XSM_DEFAULT_ARG const struct domain *d)
>>>>    {
>>>> -    return 0;
>>>> +    XSM_ASSERT_ACTION(XSM_HOOK);
>>>> +    return xsm_default_action(action, current->domain, d);
>>>
>>> Similarly:
>>>       return xsm_default_action(action, d, NULL);
>>>
>>> The single call is:
>>> xsm_argo_register_any_source(currd);
>>
>> There being just a single call puts this on the edge. If there was another
>> one not passing current->domain, I think the same argument as above would
>> hold here. And the general concept is what I think should matter when
>> writing the dummy implementations.
> 
> For flask, we have xen as the target again:
>      allow domain_type xen_t:argo register_any_source;
> 
> ... since a wildcard ring doesn't have a known target domain.
> 
>>> These argo hooks all pass in their arguments explicitly, so I think we
>>> should do that and not use current.  (The send and register hooks could
>>> use current, and that could make sense as those map to hypercalls.  But
>>> it is correct today with the explicit arguments.)
>>>
>>> With the changes:
>>> Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
>>
>> Thanks, but no - unless I misunderstand how permissions are intended to
>> work here, I don't think I can make the changes requested, and hence I
>> can't apply the R-b.
> Understandable.
> 
> It seems to me that the XSM hooks have two styles.  Either implicit args 
> (using current) or explicit args.  Today, the argo hooks take explicit 
> like the grant hooks for instance.

Yes, which doesn't make things any easier. I follow your argumentation as
one of the possible interpretations, but I think I really need Daniel's
verdict (as XSM maintainer) here in order to know whether to adjust the
proposed code. (It is true that what you suggest comes closer to the
blanket "return 0" that were previously there in all the Argo hooks,
leaving aside that due to it being XSM_HOOK all of this is cosmetic / doc
only anyway. There is certainly also the option to retain those, but it
feels that doing it like this was wrong from the start.)

Jan