From 901e269fd5b5d6868b4055f4b8afcf876cf5c8bd Mon Sep 17 00:00:00 2001 From: Nicolin Chen Date: Thu, 31 Jul 2025 20:01:27 -0700 Subject: iommu/arm-smmu-v3: Fix smmu_domain->nr_ats_masters decrement The arm_smmu_attach_commit() updates master->ats_enabled before calling arm_smmu_remove_master_domain() that is supposed to clean up everything in the old domain, including the old domain's nr_ats_masters. So, it is supposed to use the old ats_enabled state of the device, not an updated state. This isn't a problem if switching between two domains where: - old ats_enabled = false; new ats_enabled = false - old ats_enabled = true; new ats_enabled = true but can fail cases where: - old ats_enabled = false; new ats_enabled = true (old domain should keep the counter but incorrectly decreased it) - old ats_enabled = true; new ats_enabled = false (old domain needed to decrease the counter but incorrectly missed it) Update master->ats_enabled after arm_smmu_remove_master_domain() to fix this. Fixes: 7497f4211f4f ("iommu/arm-smmu-v3: Make changing domains be hitless for ATS") Cc: stable@vger.kernel.org Signed-off-by: Nicolin Chen Acked-by: Will Deacon Reviewed-by: Jason Gunthorpe Reviewed-by: Pranjal Shrivastava Link: https://lore.kernel.org/r/20250801030127.2006979-1-nicolinc@nvidia.com Signed-off-by: Joerg Roedel --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -2997,9 +2997,9 @@ void arm_smmu_attach_commit(struct arm_s /* ATS is being switched off, invalidate the entire ATC */ arm_smmu_atc_inv_master(master, IOMMU_NO_PASID); } - master->ats_enabled = state->ats_enabled; arm_smmu_remove_master_domain(master, state->old_domain, state->ssid); + master->ats_enabled = state->ats_enabled; } static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)