Subject: Re: [PATCH rc v2 1/5] iommu/arm-smmu-v3: Add arm_smmu_adopt_strtab() for kdump

From: Jason Gunthorpe <[email-masked]>
Date: Fri, 24 Apr 2026 13:56:13 -0300

On Wed, Apr 15, 2026 at 02:17:36PM -0700, Nicolin Chen wrote:
> +static int arm_smmu_adopt_strtab_2lvl(struct arm_smmu_device *smmu, u32 cfg_reg,
> +				      dma_addr_t dma)
> +{
> +	u32 log2size = FIELD_GET(STRTAB_BASE_CFG_LOG2SIZE, cfg_reg);
> +	u32 split = FIELD_GET(STRTAB_BASE_CFG_SPLIT, cfg_reg);
> +	struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg;
> +	u32 num_l1_ents;
> +	int i;
> +
> +	if (log2size < split) {
> +		dev_err(smmu->dev, "kdump: invalid log2size %u < split %u\n",
> +			log2size, split);
> +		return -EINVAL;
> +	}
> +
> +	if (split != STRTAB_SPLIT) {
> +		dev_err(smmu->dev,
> +			"kdump: unsupported STRTAB_SPLIT %u (expected %u)\n",
> +			split, STRTAB_SPLIT);
> +		return -EINVAL;
> +	}
> +
> +	num_l1_ents = 1 << (log2size - split);
> +	cfg->l2.l1_dma = dma;
> +	cfg->l2.num_l1_ents = num_l1_ents;
> +	cfg->l2.l1tab = devm_memremap(
> +		smmu->dev, dma, num_l1_ents * sizeof(struct arm_smmu_strtab_l1),
> +		MEMREMAP_WB);

WB shouldn't be unconditional? If the SMMU is working non-coherently
we need to map it NC. Same remark everwhere

Jason