Re: [PATCH 1/3] iommu/qcom: Invalidate the TLB in flush_iotlb_all

[Yijie Yang <yijie.yang@oss.qualcomm.com>]

On 10/31/2026 6:04 AM, Dmitry Baryshkov wrote:
> qcom_iommu_flush_iotlb_all() only waits for a TLB sync and never
> invalidates anything. iommu_unmap() users do not notice, since
> io-pgtable invalidates each page through the gather, but drm/msm unmaps
> with a NULL gather and relies on flush_iotlb_all. On db410c the GPU then
> hangs on stale TLB entries as soon as another process reuses the IOVAs.
> 
> Invalidate the whole context, as arm-smmu does, and keep iotlb_sync a
> plain sync.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> ---
>   drivers/iommu/arm/arm-smmu/qcom_iommu.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> index 21d18ce67b98..54130c32056a 100644
> --- a/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> +++ b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> @@ -479,14 +479,22 @@ static void qcom_iommu_flush_iotlb_all(struct iommu_domain *domain)
>   		return;
>   
>   	pm_runtime_get_sync(qcom_domain->iommu->dev);
> -	qcom_iommu_tlb_sync(pgtable->cookie);
> +	qcom_iommu_tlb_inv_context(pgtable->cookie);
>   	pm_runtime_put_sync(qcom_domain->iommu->dev);
>   }
>   
>   static void qcom_iommu_iotlb_sync(struct iommu_domain *domain,
>   				  struct iommu_iotlb_gather *gather)
>   {
> -	qcom_iommu_flush_iotlb_all(domain);
> +	struct qcom_iommu_domain *qcom_domain = to_qcom_iommu_domain(domain);
> +	struct io_pgtable *pgtable = container_of(qcom_domain->pgtbl_ops,
> +						  struct io_pgtable, ops);
> +	if (!qcom_domain->pgtbl_ops)
> +		return;
> +
> +	pm_runtime_get_sync(qcom_domain->iommu->dev);
> +	qcom_iommu_tlb_sync(pgtable->cookie);
Optional cleanup: pgtable->cookie is already qcom_domain. Could both 
callbacks pass it directly to the TLB helpers and drop the pgtable 
variable and container_of() lookup?

> +	pm_runtime_put_sync(qcom_domain->iommu->dev);
>   }
>   
>   static phys_addr_t qcom_iommu_iova_to_phys(struct iommu_domain *domain,
> 

-- 
Best Regards,
Yijie