[PATCH v5 03/27] iommu/arm-smmu-v3: Add a type for the CD entry

[Moritz Fischer]

On Wed, Mar 13, 2024 at 05:44:35PM +0800, Michael Shavit wrote:
> On Tue, Mar 5, 2024 at 7:44 AM Jason Gunthorpe <jgg at nvidia.com> wrote:
> >
> > Instead of passing a naked __le16 * around to represent a CD table entry
> > wrap it in a "struct arm_smmu_cd" with an array of the correct size.  
> This
> > makes it much clearer which functions will comprise the "CD API".
> >
> > Tested-by: Nicolin Chen <nicolinc at nvidia.com>
> > Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
> > ---
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 20 +++++++++++---------
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  7 ++++++-
> >  2 files changed, 17 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c  
> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > index 9e9233331c4636..c60b067c1f553e 100644
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > @@ -1219,7 +1219,8 @@ static void arm_smmu_write_cd_l1_desc(__le64 *dst,
> >         WRITE_ONCE(*dst, cpu_to_le64(val));
> >  }
> >
> > -static __le64 *arm_smmu_get_cd_ptr(struct arm_smmu_master *master, u32  
> ssid)
> > +static struct arm_smmu_cd *arm_smmu_get_cd_ptr(struct arm_smmu_master  
> *master,
> > +                                              u32 ssid)
> >  {
> >         __le64 *l1ptr;
> >         unsigned int idx;
> > @@ -1228,7 +1229,8 @@ static __le64 *arm_smmu_get_cd_ptr(struct  
> arm_smmu_master *master, u32 ssid)
> >         struct arm_smmu_ctx_desc_cfg *cd_table = &master->cd_table;
> >
> >         if (cd_table->s1fmt == STRTAB_STE_0_S1FMT_LINEAR)
> > -               return cd_table->cdtab + ssid * CTXDESC_CD_DWORDS;
> > +               return (struct arm_smmu_cd *)(cd_table->cdtab +
> > +                                             ssid * CTXDESC_CD_DWORDS);

> Can we define cd_table.cdtab as a union type to avoid this cast and
> make the struct definition more explicit?

+1, I think that'd make it more readable.

> >
> >         idx = ssid >> CTXDESC_SPLIT;
> >         l1_desc = &cd_table->l1_desc[idx];
> > @@ -1242,7 +1244,7 @@ static __le64 *arm_smmu_get_cd_ptr(struct  
> arm_smmu_master *master, u32 ssid)
> >                 arm_smmu_sync_cd(master, ssid, false);
> >         }
> >         idx = ssid & (CTXDESC_L2_ENTRIES - 1);
> > -       return l1_desc->l2ptr + idx * CTXDESC_CD_DWORDS;
> > +       return &l1_desc->l2ptr[idx];
> >  }
> >
> >  int arm_smmu_write_ctx_desc(struct arm_smmu_master *master, int ssid,
> > @@ -1261,7 +1263,7 @@ int arm_smmu_write_ctx_desc(struct  
> arm_smmu_master *master, int ssid,
> >          */
> >         u64 val;
> >         bool cd_live;
> > -       __le64 *cdptr;
> > +       struct arm_smmu_cd *cdptr;
> >         struct arm_smmu_ctx_desc_cfg *cd_table = &master->cd_table;
> >         struct arm_smmu_device *smmu = master->smmu;
> >
> > @@ -1272,7 +1274,7 @@ int arm_smmu_write_ctx_desc(struct  
> arm_smmu_master *master, int ssid,
> >         if (!cdptr)
> >                 return -ENOMEM;
> >
> > -       val = le64_to_cpu(cdptr[0]);
> > +       val = le64_to_cpu(cdptr->data[0]);
> >         cd_live = !!(val & CTXDESC_CD_0_V);
> >
> >         if (!cd) { /* (5) */
> > @@ -1289,9 +1291,9 @@ int arm_smmu_write_ctx_desc(struct  
> arm_smmu_master *master, int ssid,
> >                  * this substream's traffic
> >                  */
> >         } else { /* (1) and (2) */
> > -               cdptr[1] = cpu_to_le64(cd->ttbr &  
> CTXDESC_CD_1_TTB0_MASK);
> > -               cdptr[2] = 0;
> > -               cdptr[3] = cpu_to_le64(cd->mair);
> > +               cdptr->data[1] = cpu_to_le64(cd->ttbr &  
> CTXDESC_CD_1_TTB0_MASK);
> > +               cdptr->data[2] = 0;
> > +               cdptr->data[3] = cpu_to_le64(cd->mair);
> >
> >                 /*
> >                  * STE may be live, and the SMMU might read dwords of  
> this CD in any
> > @@ -1323,7 +1325,7 @@ int arm_smmu_write_ctx_desc(struct  
> arm_smmu_master *master, int ssid,
> >          *   field within an aligned 64-bit span of a structure can be  
> altered
> >          *   without first making the structure invalid.
> >          */
> > -       WRITE_ONCE(cdptr[0], cpu_to_le64(val));
> > +       WRITE_ONCE(cdptr->data[0], cpu_to_le64(val));
> >         arm_smmu_sync_cd(master, ssid, true);
> >         return 0;
> >  }
> > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h  
> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > index 23baf117e7e4b5..7078ed569fd4d3 100644
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > @@ -282,6 +282,11 @@ struct arm_smmu_ste {
> >  #define CTXDESC_L1_DESC_L2PTR_MASK     GENMASK_ULL(51, 12)
> >
> >  #define CTXDESC_CD_DWORDS              8
> > +
> > +struct arm_smmu_cd {
> > +       __le64 data[CTXDESC_CD_DWORDS];
> > +};
> > +
> >  #define CTXDESC_CD_0_TCR_T0SZ          GENMASK_ULL(5, 0)
> >  #define CTXDESC_CD_0_TCR_TG0           GENMASK_ULL(7, 6)
> >  #define CTXDESC_CD_0_TCR_IRGN0         GENMASK_ULL(9, 8)
> > @@ -591,7 +596,7 @@ struct arm_smmu_ctx_desc {
> >  };
> >
> >  struct arm_smmu_l1_ctx_desc {
> > -       __le64                          *l2ptr;
> > +       struct arm_smmu_cd              *l2ptr;
> >         dma_addr_t                      l2ptr_dma;
> >  };
> >
> > --
> > 2.43.2
> >
> >

> Reviewed-by: Michael Shavit <mshavit at google.com>

Reviewed-by: Moritz Fischer <moritzf at google.com>