Re: [PATCH rc v1 1/4] iommu/arm-smmu-v3: Add arm_smmu_adopt_strtab() for kdump

[Nicolin Chen <nicolinc@nvidia.com>]

On Thu, Apr 09, 2026 at 12:46:50PM -0700, Nicolin Chen wrote:
> +	if (fmt == STRTAB_BASE_CFG_FMT_2LVL) {
> +		/* Enforce 2-level feature flag to match the adopted table */
> +		smmu->features |= ARM_SMMU_FEAT_2_LVL_STRTAB;
> +		ret = arm_smmu_adopt_strtab_2lvl(smmu, cfg_reg, dma);
> +	} else if (fmt == STRTAB_BASE_CFG_FMT_LINEAR) {
> +		/* Force linear feature flag to match the adopted table */
> +		smmu->features &= ~ARM_SMMU_FEAT_2_LVL_STRTAB;
> +		ret = arm_smmu_adopt_strtab_linear(smmu, cfg_reg, dma);

Made a small fix here. Including it in v2.

@@ -4662,11 +4662,18 @@ static int arm_smmu_adopt_strtab(struct arm_smmu_device *smmu)
        dev_info(smmu->dev, "kdump: adopting crashed kernel's stream table\n");

        if (fmt == STRTAB_BASE_CFG_FMT_2LVL) {
-               /* Enforce 2-level feature flag to match the adopted table */
-               smmu->features |= ARM_SMMU_FEAT_2_LVL_STRTAB;
+               /*
+                * Both kernels run on the same hardware, so it's impossible for
+                * kdump kernel to see the support for linear stream table only.
+                */
+               if (WARN_ON(!(smmu->features & ARM_SMMU_FEAT_2_LVL_STRTAB)))
+                       return -EINVAL;
                ret = arm_smmu_adopt_strtab_2lvl(smmu, cfg_reg, dma);
        } else if (fmt == STRTAB_BASE_CFG_FMT_LINEAR) {
-               /* Force linear feature flag to match the adopted table */
+               /*
+                * In case that the old kernel for some reason used the linear
+                * format, enforce the same format to match the adopted table.
+                */
                smmu->features &= ~ARM_SMMU_FEAT_2_LVL_STRTAB;
                ret = arm_smmu_adopt_strtab_linear(smmu, cfg_reg, dma);
        } else {

Nicolin