linux-kernel - Re: [PATCH v7 2/4] iommu/io-pgtable-arm: Re-use the pgtable walk for iova_to

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Message-ID: <CAF6AEGvdKc3APaYVZ1G9iQfw22yb2MGssADhXU50MhZqp8tcrA@mail.gmail.com>
Date: Fri, 23 Aug 2024 10:22:10 -0700
From: Rob Clark <robdclark@...il.com>
To: Will Deacon <will@...nel.org>
Cc: iommu@...ts.linux.dev, linux-arm-msm@...r.kernel.org, 
	freedreno@...ts.freedesktop.org, Mostafa Saleh <smostafa@...gle.com>, 
	Rob Clark <robdclark@...omium.org>, Robin Murphy <robin.murphy@....com>, 
	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 v7 2/4] iommu/io-pgtable-arm: Re-use the pgtable walk for iova_to_phys

On Fri, Aug 23, 2024 at 9:11 AM Will Deacon <will@...nel.org> wrote:
>
> On Tue, Aug 20, 2024 at 10:16:45AM -0700, Rob Clark wrote:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > Re-use the generic pgtable walk path.
> >
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > ---
> >  drivers/iommu/io-pgtable-arm.c | 73 +++++++++++++++++-----------------
> >  1 file changed, 36 insertions(+), 37 deletions(-)
> >
> > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> > index b4bc358740e0..5fa1274a665a 100644
> > --- a/drivers/iommu/io-pgtable-arm.c
> > +++ b/drivers/iommu/io-pgtable-arm.c
> > @@ -710,42 +710,6 @@ static size_t arm_lpae_unmap_pages(struct io_pgtable_ops *ops, unsigned long iov
> >                               data->start_level, ptep);
> >  }
> >
> > -static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
> > -                                      unsigned long iova)
> > -{
> > -     struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
> > -     arm_lpae_iopte pte, *ptep = data->pgd;
> > -     int lvl = data->start_level;
> > -
> > -     do {
> > -             /* Valid IOPTE pointer? */
> > -             if (!ptep)
> > -                     return 0;
> > -
> > -             /* Grab the IOPTE we're interested in */
> > -             ptep += ARM_LPAE_LVL_IDX(iova, lvl, data);
> > -             pte = READ_ONCE(*ptep);
> > -
> > -             /* Valid entry? */
> > -             if (!pte)
> > -                     return 0;
> > -
> > -             /* Leaf entry? */
> > -             if (iopte_leaf(pte, lvl, data->iop.fmt))
> > -                     goto found_translation;
> > -
> > -             /* Take it to the next level */
> > -             ptep = iopte_deref(pte, data);
> > -     } while (++lvl < ARM_LPAE_MAX_LEVELS);
> > -
> > -     /* Ran out of page tables to walk */
> > -     return 0;
> > -
> > -found_translation:
> > -     iova &= (ARM_LPAE_BLOCK_SIZE(lvl, data) - 1);
> > -     return iopte_to_paddr(pte, data) | iova;
> > -}
> > -
> >  struct io_pgtable_walk_data {
> >       void                            *data;
> >       int (*visit)(struct io_pgtable_walk_data *walk_data, int lvl,
> > @@ -760,6 +724,41 @@ static int __arm_lpae_iopte_walk(struct arm_lpae_io_pgtable *data,
> >                                arm_lpae_iopte *ptep,
> >                                int lvl);
> >
> > +struct iova_to_phys_data {
> > +     arm_lpae_iopte pte;
> > +     int lvl;
> > +};
> > +
> > +static int visit_iova_to_phys(struct io_pgtable_walk_data *walk_data, int lvl,
> > +                           arm_lpae_iopte pte, size_t size)
> > +{
> > +     struct iova_to_phys_data *data = walk_data->data;
> > +     data->pte = pte;
> > +     data->lvl = lvl;
> > +     return 0;
> > +}
> > +
> > +static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
> > +                                      unsigned long iova)
> > +{
> > +     struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
> > +     struct iova_to_phys_data d;
> > +     struct io_pgtable_walk_data walk_data = {
> > +             .data = &d,
> > +             .visit = visit_iova_to_phys,
> > +             .addr = iova,
> > +             .end = iova + 1,
> > +     };
> > +     int ret;
> > +
> > +     ret = __arm_lpae_iopte_walk(data, &walk_data, data->pgd, data->start_level);
> > +     if (ret)
> > +             return 0;
> > +
> > +     iova &= (ARM_LPAE_BLOCK_SIZE(d.lvl, data) - 1);
> > +     return iopte_to_paddr(d.pte, data) | iova;
> > +}
> > +
> >  static int io_pgtable_visit(struct arm_lpae_io_pgtable *data,
> >                           struct io_pgtable_walk_data *walk_data,
> >                           arm_lpae_iopte *ptep, int lvl)
> > @@ -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))
>
> Why do you care about the selftest here?

Otherwise we see a flood of WARN_ON from negative tests in the selftests

BR,
-R

> Will