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

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

Hello Julien,


It is me again.

On 15.11.18 17:05, Julien Grall wrote:
> On 11/15/18 1:19 PM, Andrii Anisov wrote:
> > > So I would prefer to stick with _t which is quite common within the p2m
> > > code base so far.
> > I've found a similar code only in one place - p2m_get_entry()
> > function. And it is, at least, somehow commented there:
> > ...
> >      /* Allow t to be NULL */
> >      t = t ?: &_t;
> >
> >      *t = p2m_invalid;
> > ...
> And in x86 code...
I've taken care to look into the x86 p2m code about that construction.

I've found it in x86's  `p2m_get_page_from_gfn` function. And it looks 
reasonable over there. Because that value is not only might be returned 
to a caller. But is needed by the function code itself to take decisions 
and passing it to called functions (which do not do a check for the null 
pointer).

Your code (as well as `p2m_get_entry`) does not actually use that value. 
So I see no need to calculate or keep it if it is not needed by a caller.
--
Sincerely,
Andrii Anisov.


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