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

[Qinxin Xia]

On 2026/3/14 04:19:14, Nicolin Chen <nicolinc at nvidia.com> wrote:
> 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?
> 
Can we lock streams_mutex here?
>> +
>> +	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
> 
As above, I will do clean code in the next version.
-- 
Thanks,
Qinxin