linux-kernel - Re: [PATCH v8 2/4] iommu/io-pgtable-arm: Re-use the pgtable walk for iova_to

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Message-ID: <CAF6AEGtFg2D=4RVQC=YT9OsqdNwwsuJCyi=hu8Box0A6psecQA@mail.gmail.com>
Date: Tue, 27 Aug 2024 09:54:29 -0700
From: Rob Clark <robdclark@...il.com>
To: Will Deacon <will@...nel.org>
Cc: iommu@...ts.linux.dev, Robin Murphy <robin.murphy@....com>, 
	Rob Clark <robdclark@...omium.org>, Joerg Roedel <joro@...tes.org>, 
	"moderated list:ARM SMMU DRIVERS" <linux-arm-kernel@...ts.infradead.org>, 
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 2/4] iommu/io-pgtable-arm: Re-use the pgtable walk for iova_to_phys

On Tue, Aug 27, 2024 at 5:02 AM Will Deacon <will@...nel.org> wrote:
>
> On Mon, Aug 26, 2024 at 10:15:39AM -0700, Rob Clark wrote:
> > @@ -776,7 +775,7 @@ static int io_pgtable_visit(struct arm_lpae_io_pgtable *data,
> >               return 0;
> >       }
> >
> > -     if (WARN_ON(!iopte_table(pte, lvl)))
> > +     if (WARN_ON(!iopte_table(pte, lvl) && !selftest_running))
> >               return -EINVAL;
> >
> >       ptep = iopte_deref(pte, data);
>
> I still don't grok this hunk. If the selftest is running, we want to
> return -EINVAL here rather than dereference something that isn't a
> table, right?
>
> Suppressing the warning is one thing, but this seems to do more than
> that.

oh, that should be

   if (!iopte_table(...)) {
      WARN_ON(!selftest_running);
      return -EINVAL;
   }

I did boot with selftests enabled, and it didn't _seem_ to complain
about anything, so I overlooked that

BR,
-R

>
> Will