Re: [PATCH 5/8] iommu/qcom: Publish pgtbl_ops before releasing init_mutex

[Konrad Dybcio]

On 6/23/26 2:20 PM, Mukesh Ojha wrote:
> qcom_domain->pgtbl_ops was assigned after mutex_unlock(). Another thread
> calling qcom_iommu_init_domain() would see qcom_domain->iommu already set
> (domain fully initialized) and skip re-initialization under the mutex.
> If it then called qcom_iommu_map() before the first thread set pgtbl_ops,
> it would observe a NULL ops pointer and return -ENODEV for valid mappings.
> 
> Move the assignment to before mutex_unlock() so that once the mutex is
> released the domain is fully visible to concurrent operations.
> 
> Signed-off-by: Mukesh Ojha <mukesh.ojha@xxxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/arm/arm-smmu/qcom_iommu.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> index b6ce85f7f923..40fb0408dc07 100644
> --- a/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> +++ b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> @@ -306,13 +306,12 @@ static int qcom_iommu_init_domain(struct iommu_domain *domain,
>  		ctx->domain = domain;
>  	}
>  
> -	mutex_unlock(&qcom_domain->init_mutex);
> -
>  	/* Publish page table ops for map/unmap */
>  	qcom_domain->pgtbl_ops = pgtbl_ops;
>  
> -	return 0;
> +	mutex_unlock(&qcom_domain->init_mutex);

Reviewed-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>

even better, we could probably just wrap this in guard(mutex) now

Konrad