Re: [Xen-devel] page ref/type count overflows

[Gianluca Guida <gianluca.guida@xxxxxxxxxxxxx>]

Jan Beulich wrote:
> Below is what I currently have it at. I'm afraid it won't get much simpler,
> but I think it reasonably expresses the individual overlays. There are three
> more transformations I plan to make:
> - _domain -> unsigned int
> - next_shadow -> __mfn_t
> - split u into two unions (one having type_info, type/pinned/count, and
> cpumask, the other having _domain, back, and order).
>
> That last step is to avoid having to re-add __attribute__ ((__packed__)),
> so that other (future) changes to the structure won't risk mis-aligning any
> fields again.
>
> Does this look acceptable?
Personally, while I don't have (and I can't have) anything against this, 
I think that this kind of unified struct would make the shadow code more 
error-prone, by making shadow pages and guest pages being casted by the 
same type.
Of course, every bug is fixable, and good programmers shouldn't do this 
kind of errors. But I think that being able to differentiate between 
shadow's page_info and normal page_info by something more than just a 
variable name would help a lot the clarity of this already complex code.
Thanks,
Gianluca

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