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

[Mostafa Saleh <smostafa@google.com>]

On Mon, Mar 04, 2024 at 07:43:51PM -0400, Jason Gunthorpe 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@nvidia.com>
> Signed-off-by: Jason Gunthorpe <jgg@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);
>  
>  	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: Mostafa Saleh <smostafa@google.com>

Thanks,
Mostafa