Re: Fwd: [PATCH v7 1/2] x86: Add Isolated Memory Regions for Quark X1000

[Bryan O'Donoghue]

On 30/01/15 14:04, Andy Shevchenko wrote:
> > On 30/01/15 12:03, Andy Shevchenko wrote:
>
> > > When CONFIG_DEBUGFS=n, you will get error pointer here, which is not NULL.
> > >
> > > So, the proper check is
> > > if (IS_ERR())
> > >    return PTR_ERR();
> > > if (!file)
> > >    return -ENOMEM;
> >
> > Yeah I saw that. Also saw that most other code doesn't bother trapping
> > those return values - so skipped it.
> > No issue adding.
>
> Ok.
>
> > > > +               } else {
> > > > +                       reg = i;
> > >
> > > Do we go always through all IMRs and choose the last one?
> > > If no, break is missed here.
> >
> > Yep - we always choose the last one.
>
> OK.
>
> > > > +       ret = imr_check_params(base, size);
> > > > +       if (ret == -EINVAL || (ret == -ENOMEM && reg == -1))
> > >
> > > reg base size (0 correct, 1 wrong):
> > >
> > > 0 0 0 Ãââ which should be used? what is the priority?
> > > 0 x 1 Ãââ index
> > > 0 1 x Ãââ index
> > > 1 0 0 Ãââ address
> > > 1 0 1 Ãââ an error
> > > 1 1 1 Ãââ an error
> > >
> > > Thus, could it be simpler? Like
> > > if (reg < 0 && ret) ?
> >
> > ret will be EINVAL for unaligned base or size
> > ret will be ENOMEM when reg == -1 and size == 0
>
> ENOMEM only when size == 0.
>
> I have read the function description. From my point of view there is
> no difference what is in (base, size) if we have index set.

I should be clearer :)

Will change so that -ENOMEM won't be returned. ENOMEM transmits no 
useful information...

> > I could probably write it like this to make it clearer
> > (ret == -EINVAL || (reg == -1 && size == 0)
> >          return -EINVAL;
> >
> > traps unaligned input - for address range tear-down
> > traps zero sized - for address range tear-down
> >
> > Allows index based teardown i.e. reg >= 0
>
> Again, seems a logic mistake here, or description of function is not correct.
> Do we care what (base, size) if index is set? If so, why is it not
> mentioned properly in the description?

No we don't if index >= 0 base and size are ignored => teardown by index.

I'll make that clear in a comment with the refactored statement above. 
-ENOMEM is redundant

--
BOD
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