Re: [Xen-devel] [PATCH 2/2] dom_cow is needed for mem-sharing only

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.05.19 at 11:52, <julien.grall@xxxxxxx> wrote:
> On 5/31/19 10:49 AM, Jan Beulich wrote:
>>>>> On 31.05.19 at 11:42, <julien.grall@xxxxxxx> wrote:
>>> On 5/31/19 10:35 AM, Jan Beulich wrote:
>>>> --- a/xen/include/xen/mm.h
>>>> +++ b/xen/include/xen/mm.h
>>>> @@ -644,6 +644,9 @@ static inline void filtered_flush_tlb_ma
>>>>    
>>>>    /* Private domain structs for DOMID_XEN, DOMID_IO, etc. */
>>>>    extern struct domain *dom_xen, *dom_io, *dom_cow;
>>>
>>> Don't you want to protect dom_cow with "#ifdef CONFIG_HAS_MEM_SHARING"?
>> 
>> There's no need to with ...
>> 
>>>> +#ifndef CONFIG_HAS_MEM_SHARING
>>>> +# define dom_cow NULL
>>>> +#endif
>> 
>> ... this, and this way there's less clutter overall.
> 
> I am all for avoiding cluttering but not at the expense of making the 
> code less intuitive. In this case, I would prefer the decleration 
> dom_cow to be guarded.

While it would be easy enough to do, I fail to see how the chosen
construct is not "intuitive". In fact I don't think this would be the
first instance of a #define overriding a prior declaration. Doing so
utilizes one of the very basic C preprocessor principles.

Jan



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