Re: [PATCH RFC v5 4/6] iommu/arm-smmu-v3: Support shared SIDs in insert/remove_master

[Nicolin Chen <nicolinc@nvidia.com>]

On Tue, Oct 06, 2026 at 08:19:10PM +0800, Peng Fan (OSS) wrote:
> @@ -4193,17 +4213,31 @@ static void arm_smmu_remove_master(struct arm_smmu_master *master)
>  		return;
>  
>  	mutex_lock(&smmu->streams_mutex);
> -	for (i = 0; i < master->num_streams; i++) {
> -		int j;
> +	if (!list_empty(&master->shared_masters_elm)) {
> +		struct arm_smmu_stream *stream = master->streams[0];
>  
> -		/* Skip duplicated SID pointers already freed */
> -		for (j = 0; j < i; j++)
> -			if (master->streams[j] == master->streams[i])
> -				break;
> -		if (j < i)
> -			continue;
> -		rb_erase(&master->streams[i]->node, &smmu->streams);
> -		kfree(master->streams[i]);
> +		list_del_init(&master->shared_masters_elm);
> +		if (list_is_singular(&stream->shared_masters)) {
> +			struct arm_smmu_master *last;
> +
> +			last = list_first_entry(&stream->shared_masters,
> +					struct arm_smmu_master,
> +					shared_masters_elm);
> +			list_del_init(&last->shared_masters_elm);
> +		}

This doesn't look right: it still needs the for loop and also needs
to compare master with stream->master:

		if (!list_empty(&stream->shared_masters)) {
			struct arm_smmu_master *next;

			list_del_init(&master->shared_masters_elm);
			next = list_first_entry(&stream->shared_masters,
						struct arm_smmu_master,
						shared_masters_elm);
			if (stream->master == master)
				stream->master = next;
			if (list_is_singular(&stream->shared_masters))
				list_del_init(&next->shared_masters_elm);
			continue;
		}
		rb_erase(&stream->node, &smmu->streams);
		kfree(stream);

Nicolin