Commit a82efb87 authored Mar 17, 2026 by Shameer Kolothum Committed by Joerg Roedel Mar 17, 2026

iommu: Add device ATS supported capability



PCIe ATS may be disabled by platform firmware, root complex limitations,
or kernel policy even when a device advertises the ATS capability in its
PCI configuration space.

Add a new IOMMU_CAP_PCI_ATS_SUPPORTED capability to allow IOMMU drivers
to report the effective ATS decision for a device.

When this capability is true for a device, ATS may be enabled for that
device, but it does not imply that ATS is currently enabled.

A subsequent patch will extend iommufd to expose the effective ATS
status to userspace.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

parent d6c65b0f

drivers/iommu/amd/iommu.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -2985,6 +2985,12 @@ static bool amd_iommu_capable(struct device *dev, enum iommu_cap cap)

		return amd_iommu_hd_support(iommu);
		}
		case IOMMU_CAP_PCI_ATS_SUPPORTED: {
		struct iommu_dev_data *dev_data = dev_iommu_priv_get(dev);

		return amd_iommu_iotlb_sup &&
		(dev_data->flags & AMD_IOMMU_DEVICE_FLAG_ATS_SUP);
		}
		default:
		break;
		}

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -107,6 +107,7 @@ static const char * const event_class_str[] = {
		};

		static int arm_smmu_alloc_cd_tables(struct arm_smmu_master *master);
		static bool arm_smmu_ats_supported(struct arm_smmu_master *master);

		static void parse_driver_options(struct arm_smmu_device *smmu)
		{
		@@ -2494,6 +2495,8 @@ static bool arm_smmu_capable(struct device *dev, enum iommu_cap cap)
		return true;
		case IOMMU_CAP_DIRTY_TRACKING:
		return arm_smmu_dbm_capable(master->smmu);
		case IOMMU_CAP_PCI_ATS_SUPPORTED:
		return arm_smmu_ats_supported(master);
		default:
		return false;
		}

drivers/iommu/intel/iommu.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -3220,6 +3220,8 @@ static bool intel_iommu_capable(struct device *dev, enum iommu_cap cap)
		return ecap_sc_support(info->iommu->ecap);
		case IOMMU_CAP_DIRTY_TRACKING:
		return ssads_supported(info->iommu);
		case IOMMU_CAP_PCI_ATS_SUPPORTED:
		return info->ats_supported;
		default:
		return false;
		}

include/linux/iommu.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -272,6 +272,8 @@ enum iommu_cap {
		*/
		IOMMU_CAP_DEFERRED_FLUSH,
		IOMMU_CAP_DIRTY_TRACKING, /* IOMMU supports dirty tracking */
		/* ATS is supported and may be enabled for this device */
		IOMMU_CAP_PCI_ATS_SUPPORTED,
		};

		/* These are the possible reserved region types */