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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.08.17 at 02:51, <blackskygg@xxxxxxxxx> wrote:
> 2017-08-23 17:55 GMT+08:00 Jan Beulich <JBeulich@xxxxxxxx>:
>>>>> On 22.08.17 at 20:08, <blackskygg@xxxxxxxxx> 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)?

Jan


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