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

[Michael Shavit]

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?

>
>         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>