Re: [Xen-devel] [PATCH v6 1/7] xen: xsm: flask: introduce XENMAPSPACE_gmfn_share for memory sharing

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.08.18 at 22:57, <sstabellini@xxxxxxxxxx> wrote:
> On Thu, 2 Aug 2018, Jan Beulich wrote:
>> >> > +/*
>> >> > + * This action also requires that @current targets @d, but it has 
>> >> > already been
>> >> > + * checked somewhere higher in the call stack.
>> >> 
>> >> I'm not convinced it is a good idea to have such a dependency, even
>> >> more so with this cloudy a reference. If there's another XSM check
>> >> that has necessarily been done before, you should at least name it
>> >> here so it's easy to later verify that the assumption still holds. But
>> >> even better would imo be to re-do the check here, just in case.
>> > 
>> > I am fine with that. It should be just a matter of doing the following,
>> > right?
>> > 
>> > static XSM_INLINE int xsm_map_gmfn_share(XSM_DEFAULT_ARG struct domain *d,
>> >                                          struct domain *t)
>> > {
>> >     XSM_ASSERT_ACTION(XSM_TARGET);
>> >     return xsm_default_action(XSM_TARGET, current->domain, d) &&
>> >            xsm_default_action(action, current->domain, t);
>> 
>> Not exactly - xsm_default_action() doesn't return boolean, nor should
>> the function here.
> 
> You are right, zero is success. So something like the following:
> 
>     int rc = xsm_default_action(XSM_TARGET, current->domain, d);
>     if ( rc )
>         return rc;
>     return xsm_default_action(action, current->domain, t);

Didn't you inherit the patch from someone? I think we had already
arrived at

    return xsm_default_action(XSM_TARGET, current->domain, d)
            ?: xsm_default_action(action, current->domain, t);

Jan



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