Re: [RFC PATCH 3/5] iommu/arm-smmu-v3: Add Stream Table Entry display to debugfs

[Nicolin Chen <nicolinc@nvidia.com>]

On Fri, Mar 13, 2026 at 06:43:49PM +0800, Qinxin Xia wrote:
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-debugfs.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-debugfs.c
> @@ -43,6 +49,8 @@
>   */
>  
>  #include <linux/debugfs.h>
> +#include <linux/pci.h>

It doesn't seem being used (yet).

> +static struct arm_smmu_ste *smmu_get_ste(struct arm_smmu_device *smmu, u32 sid)
> +{
> +	struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg;
> +
> +	if (sid >= (1 << smmu->sid_bits))
> +		return NULL;
> +
> +	if (smmu->features & ARM_SMMU_FEAT_2_LVL_STRTAB) {
> +		u32 l1_idx = arm_smmu_strtab_l1_idx(sid);
> +		u32 l2_idx = arm_smmu_strtab_l2_idx(sid);
> +
> +		if (l1_idx >= cfg->l2.num_l1_ents || !cfg->l2.l2ptrs[l1_idx])
> +			return NULL;
> +
> +		return &cfg->l2.l2ptrs[l1_idx]->stes[l2_idx];
> +	}
> +
> +	return &cfg->linear.table[sid];
> +}

arm_smmu_get_step_for_sid() instead?

> +/**
> + * smmu_debug_dump_ste() - Dump STE details to seq_file
> + * @seq: seq_file to write to
> + * @dev: device associated with the STE
> + */
> +static void smmu_debug_dump_ste(struct seq_file *seq, struct device *dev)
> +{
> +	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
> +	struct arm_smmu_device *smmu;
> +	struct arm_smmu_ste *ste;
> +	u32 sid, cfg;
> +	int i;
> +
> +	if (!master || !master->smmu) {
> +		seq_puts(seq, "No SMMU master data\n");
> +		return;
> +	}
> +
> +	smmu = master->smmu;
> +
> +	/* Use first stream ID for debug */
> +	if (master->num_streams == 0) {
> +		seq_puts(seq, "No streams configured for device\n");
> +		return;
> +	}
> +	sid = master->streams[0].id;

These might race with release_device that would destroy master?

> +
> +	if (sid >= (1 << smmu->sid_bits)) {
> +		seq_printf(seq, "Invalid Stream ID: %u (max %u)\n",
> +			   sid, (1 << smmu->sid_bits) - 1);
> +		return;
> +	}

arm_smmu_sid_in_range() instead?

> +/* STE debugfs file operations */
> +static int smmu_debugfs_ste_show(struct seq_file *seq, void *v)
> +{
> +	struct device *dev = seq->private;
> +
> +	smmu_debug_dump_ste(seq, dev);
> +	return 0;

Could unwrap smmu_debug_dump_ste().

Nicolin