Re: [PATCH 4/6] xsm: flask: change the interface and default policy for xsm_map_gmfn_foregin

[Zhongze Liu <blackskygg@gmail.com>]

Hi Jan,

2017-08-24 14:37 GMT+08:00 Jan Beulich <JBeulich@suse.com>:
>>>> On 24.08.17 at 02:51, <blackskygg@gmail.com> wrote:
>> 2017-08-23 17:55 GMT+08:00 Jan Beulich <JBeulich@suse.com>:
>>>>>> On 22.08.17 at 20:08, <blackskygg@gmail.com> wrote:
>>>> --- a/xen/include/xsm/dummy.h
>>>> +++ b/xen/include/xsm/dummy.h
>>>> @@ -525,10 +525,12 @@ static XSM_INLINE int xsm_remove_from_physmap(XSM_DEFAULT_ARG struct domain *d1,
>>>>      return xsm_default_action(action, d1, d2);
>>>>  }
>>>>
>>>> -static XSM_INLINE int xsm_map_gmfn_foreign(XSM_DEFAULT_ARG struct domain *d, struct domain *t)
>>>> +static XSM_INLINE int xsm_map_gmfn_foreign(XSM_DEFAULT_ARG struct domain *cd,
>>>> +                                           struct domain *d, struct domain *t)
>>>>  {
>>>>      XSM_ASSERT_ACTION(XSM_TARGET);
>>>> -    return xsm_default_action(action, d, t);
>>>> +    return xsm_default_action(action, cd, d) ||
>>>> +        xsm_default_action(action, cd, t);
>>>>  }
>>>
>>> ... you use "or" here and ...
>>
>> This might be confusing. But think of returning 0 as "allowed", the
>> only condition where this
>> statement returns a 0 is when both calls return 0 -- so it's actually
>> an "and". (Think of de-morgan's law.)
>>
>> But as Stefano has pointed out, I should preserve the error code.
>
> Ah, right - the code as written suggests boolean return values,
> which gives it the wrong look. You really mean ?: instead of ||.
> Why do you, btw, pass in current->domain (as cd) instead of
> obtaining it here (just like various other hooks do)?

This was my original plan, but I'm not very sure about this, so I turn
to Julien for help, and...
Here is part of the irc log from a discussion with Julien on
#xendevel, where Julien said:

   blackskygg: I think you want to pass the current domain in
parameter, i.e having 3 domains argument.
   because your solution only works when XSM is not enabled (this is
the dummy callback)
   when XSM is enabled, the policy would be specificed by the administrator
   he needs to be able to know which domain was doing the configuration.

Cheers,

Zhongze Liu
>
> Jan
>

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