Re: [PATCH 1/7] iommu/arm-smmu-v3: Split struct arm_smmu_strtab_cfg.strtab

[Mostafa Saleh <smostafa@google.com>]

Hi Jason,

On Mon, Jun 03, 2024 at 07:31:27PM -0300, Jason Gunthorpe wrote:
> This is being used as both an array of STEs and an array of L1
> descriptors.
> 
> Give the two usages different names and correct types.
> 
> Remove STRTAB_STE_DWORDS as most usages were indexing or sizing an array
> of struct arm_smmu_ste.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 21 +++++++++------------
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  9 +++++----
>  2 files changed, 14 insertions(+), 16 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 ab415e107054c1..6b4f1a664288db 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -1661,8 +1661,8 @@ static int arm_smmu_init_l2_strtab(struct arm_smmu_device *smmu, u32 sid)
>  	if (desc->l2ptr)
>  		return 0;
>  
> -	size = 1 << (STRTAB_SPLIT + ilog2(STRTAB_STE_DWORDS) + 3);
> -	strtab = &cfg->strtab[(sid >> STRTAB_SPLIT) * STRTAB_L1_DESC_DWORDS];

I believe also STRTAB_L1_DESC_DWORDS isn’t needed as l1_desc has the same size.
Especially I already see sizeof(*cfg->l1_desc) used in some places instead of the macro.
So we can remove it also as STRTAB_STE_DWORDS.

> +	size = (1 << STRTAB_SPLIT) * sizeof(struct arm_smmu_ste);
> +	strtab = &cfg->strtab.l1_desc[sid >> STRTAB_SPLIT];
>  
>  	desc->span = STRTAB_SPLIT + 1;
>  	desc->l2ptr = dmam_alloc_coherent(smmu->dev, size, &desc->l2ptr_dma,
> @@ -2409,8 +2409,7 @@ arm_smmu_get_step_for_sid(struct arm_smmu_device *smmu, u32 sid)
>  		return &cfg->l1_desc[idx1].l2ptr[idx2];
>  	} else {
>  		/* Simple linear lookup */
> -		return (struct arm_smmu_ste *)&cfg
> -			       ->strtab[sid * STRTAB_STE_DWORDS];
> +		return &cfg->strtab.linear[sid];
>  	}
>  }
>  
> @@ -3225,17 +3224,15 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu)
>  {
>  	unsigned int i;
>  	struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg;
> -	void *strtab = smmu->strtab_cfg.strtab;
>  
>  	cfg->l1_desc = devm_kcalloc(smmu->dev, cfg->num_l1_ents,
>  				    sizeof(*cfg->l1_desc), GFP_KERNEL);
>  	if (!cfg->l1_desc)
>  		return -ENOMEM;
>  
> -	for (i = 0; i < cfg->num_l1_ents; ++i) {
> -		arm_smmu_write_strtab_l1_desc(strtab, &cfg->l1_desc[i]);
> -		strtab += STRTAB_L1_DESC_DWORDS << 3;
> -	}
> +	for (i = 0; i < cfg->num_l1_ents; ++i)
> +		arm_smmu_write_strtab_l1_desc(
> +			&smmu->strtab_cfg.strtab.l1_desc[i], &cfg->l1_desc[i]);
>  
>  	return 0;
>  }
> @@ -3267,7 +3264,7 @@ static int arm_smmu_init_strtab_2lvl(struct arm_smmu_device *smmu)
>  			l1size);
>  		return -ENOMEM;
>  	}
> -	cfg->strtab = strtab;
> +	cfg->strtab.l1_desc = strtab;
>  
>  	/* Configure strtab_base_cfg for 2 levels */
>  	reg  = FIELD_PREP(STRTAB_BASE_CFG_FMT, STRTAB_BASE_CFG_FMT_2LVL);
> @@ -3285,7 +3282,7 @@ static int arm_smmu_init_strtab_linear(struct arm_smmu_device *smmu)
>  	u32 size;
>  	struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg;
>  
> -	size = (1 << smmu->sid_bits) * (STRTAB_STE_DWORDS << 3);
> +	size = (1 << smmu->sid_bits) * sizeof(cfg->strtab.linear[0]);

nit: maybe be consistent with "sizeof(struct arm_smmu_ste)" which was used earlier
this patch and "sizeof(cfg->strtab.linear[0])"

>  	strtab = dmam_alloc_coherent(smmu->dev, size, &cfg->strtab_dma,
>  				     GFP_KERNEL);
>  	if (!strtab) {
> @@ -3294,7 +3291,7 @@ static int arm_smmu_init_strtab_linear(struct arm_smmu_device *smmu)
>  			size);
>  		return -ENOMEM;
>  	}
> -	cfg->strtab = strtab;
> +	cfg->strtab.linear = strtab;
>  	cfg->num_l1_ents = 1 << smmu->sid_bits;
>  
>  	/* Configure strtab_base_cfg for a linear table covering all SIDs */
> 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 1242a086c9f948..4769780259affc 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -206,10 +206,8 @@
>  #define STRTAB_L1_DESC_SPAN		GENMASK_ULL(4, 0)
>  #define STRTAB_L1_DESC_L2PTR_MASK	GENMASK_ULL(51, 6)
>  
> -#define STRTAB_STE_DWORDS		8
> -
>  struct arm_smmu_ste {
> -	__le64 data[STRTAB_STE_DWORDS];
> +	__le64 data[8];
>  };
>  
>  #define STRTAB_STE_0_V			(1UL << 0)
> @@ -612,7 +610,10 @@ struct arm_smmu_s2_cfg {
>  };
>  
>  struct arm_smmu_strtab_cfg {
> -	__le64				*strtab;
> +	union {
> +		struct arm_smmu_ste *linear;
> +		__le64 *l1_desc;

I agree with Nicolin, that it is confusing to have both l1_desc,
I guess a rename is sufficient.

> +	} strtab;
>  	dma_addr_t			strtab_dma;
>  	struct arm_smmu_strtab_l1_desc	*l1_desc;
>  	unsigned int			num_l1_ents;
> -- 
> 2.45.2
> 

Thanks,
Mostafa