Re: [Xen-devel] [PATCH v5 10/12] arm/mem_access: Add long-descriptor based gpt

[Julien Grall <julien.grall@xxxxxxx>]

On 06/07/17 12:18, Sergej Proskurin wrote:
> Hi Julien,
>
>
> On 07/04/2017 07:06 PM, Julien Grall wrote:
> > Hi Sergej,
> >
> >
> > > +    /*
> > > +     * According to to ARM DDI 0487B.a J1-5927, we return an error
> > > if the found
> > > +     * PTE is invalid or holds a reserved entry (PTE<1:0> == x0)) or
> > > if the PTE
> > > +     * maps a memory block at level 3 (PTE<1:0> == 01).
> > > +     */
> > > +    if ( !lpae_valid(pte) || ((level == 3) && !lpae_page(pte, level)) )
> > NIT: What you want to check here is either the entry is a superpage or
> > a page. So the below check would be easier to parse:
> >
> > if ( !lpae_is_superpage(pte, level) || !lpae_is_page(pte, level) )
> Your suggested check is easier to parse, however introduces a bug
> because as soon as the pte is not a superpage it will return an -EFAULT
> at this point. I have changed the || into an && which makes it fine
> again. The next patch series will follow shortly.
Whoops. You are right :).

Cheers,

> Cheers
> ~Sergej
--
Julien Grall

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