From mboxrd@z Thu Jan  1 00:00:00 1970
From: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Subject: Re: [RFC PATCH v1] iommu/io-pgtable-arm-v7s: Check for leaf entry
	right after finding it
Date: Fri, 24 Feb 2017 15:18:23 +0000
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To: Oleksandr Tyshchenko <olekstysh-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko-uRwfk40T5oI@public.gmane.org>, Volodymyr Babchuk <vlad.babchuk-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Andrii Anisov <andrii.anisov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Oleksandr Andrushchenko <andr2000-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, al1img <al1img-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Artem Mygaiev <joculator-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
List-Id: iommu@lists.linux-foundation.org

On Tue, Feb 21, 2017 at 03:31:26PM +0200, Oleksandr Tyshchenko wrote:
> On Tue, Feb 21, 2017 at 2:00 PM, Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org> wrote:
> > Would it not be more logical (and simpler) to just check that the thing
> > we dereference is valid to dereference when we dereference it? i.e.:
> >
> > -----8<-----
> > diff --git a/drivers/iommu/io-pgtable-arm-v7s.c
> > b/drivers/iommu/io-pgtable-arm-v7s.c
> > index 0769276c0537..f3112f9ff494 100644
> > --- a/drivers/iommu/io-pgtable-arm-v7s.c
> > +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> > @@ -418,8 +418,10 @@ static int __arm_v7s_map(struct arm_v7s_io_pgtable
> > *data, unsigned long iova,
> >                         pte |= ARM_V7S_ATTR_NS_TABLE;
> >
> >                 __arm_v7s_set_pte(ptep, pte, 1, cfg);
> > -       } else {
> > +       } else if (ARM_V7S_PTE_IS_TABLE(pte, lvl)) {
> >                 cptep = iopte_deref(pte, lvl);
> > +       } else {
> > +               return -EEXIST;
> >         }
> >
> >         /* Rinse, repeat */
> > ----->8-----
> 
> Agree. Sounds reasonable.
> 
> >
> > I think the equivalent could be done in LPAE as well.
> 
> OK.
> 
> I will resend both modified patches without RFC prefix, right?

Sounds good to me.

Will