Re: [Xen-devel] [PATCH 4/8] xen/arm: Add support for read-only foreign mappings

[Julien Grall <julien.grall@xxxxxxx>]

On 11/15/18 11:33 AM, Andrii Anisov wrote:
> Hello Julien,
Hi,

> вт, 6 лист. 2018 о 21:16 Julien Grall <julien.grall@xxxxxxx> пише:
> > @@ -275,7 +280,38 @@ struct page_info *p2m_get_page_from_gfn(struct domain *d, 
> > gfn_t gfn,
> >   static inline struct page_info *get_page_from_gfn(
> >       struct domain *d, unsigned long gfn, p2m_type_t *t, p2m_query_t q)
> >   {
> > -    return p2m_get_page_from_gfn(d, _gfn(gfn), t);
> > +    mfn_t mfn;
> > +    p2m_type_t _t;
> Me personally, do not like introducing intermediate `_t` variable.
> IMO, constructs like following:
>
> > +    if ( !t )
> > +        t = &_t;
> > +
> > +    *t = p2m_invalid;
> make the code harder to understand than simple checking `t` for nul
> before assigning it a
> value.
If I drop _t then I need to add if ( *t ) in 3 places in that code. So I 
don't think the approach is any better.
Feel free to suggest a solution that does not require to check 't' 
everywhere.
Cheers,

--
Julien Grall

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