iommufd: Add capabilities to IOMMU_GET_HW_INFO

Extend IOMMUFD_CMD_GET_HW_INFO op to query generic iommu capabilities for a
given device.

Capabilities are IOMMU agnostic and use device_iommu_capable() API passing
one of the IOMMU_CAP_*. Enumerate IOMMU_CAP_DIRTY_TRACKING for now in the
out_capabilities field returned back to userspace.

Link: https://lore.kernel.org/r/20231024135109.73787-9-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/iommu/iommufd/device.c

@@ -1185,6 +1185,10 @@ int iommufd_get_hw_info(struct iommufd_ucmd *ucmd)
 	 */
 	cmd->data_len = data_len;
 
+	cmd->out_capabilities = 0;
+	if (device_iommu_capable(idev->dev, IOMMU_CAP_DIRTY_TRACKING))
+		cmd->out_capabilities |= IOMMU_HW_CAP_DIRTY_TRACKING;
+
 	rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
 out_free:
 	kfree(data);

include/uapi/linux/iommufd.h

@@ -418,6 +418,20 @@ enum iommu_hw_info_type {
 	IOMMU_HW_INFO_TYPE_INTEL_VTD,
 };
 
+/**
+ * enum iommufd_hw_capabilities
+ * @IOMMU_HW_CAP_DIRTY_TRACKING: IOMMU hardware support for dirty tracking
+ *                               If available, it means the following APIs
+ *                               are supported:
+ *
+ *                                   IOMMU_HWPT_GET_DIRTY_BITMAP
+ *                                   IOMMU_HWPT_SET_DIRTY_TRACKING
+ *
+ */
+enum iommufd_hw_capabilities {
+	IOMMU_HW_CAP_DIRTY_TRACKING = 1 << 0,
+};
+
 /**
  * struct iommu_hw_info - ioctl(IOMMU_GET_HW_INFO)
  * @size: sizeof(struct iommu_hw_info)
@@ -429,6 +443,8 @@ enum iommu_hw_info_type {
  *             the iommu type specific hardware information data
  * @out_data_type: Output the iommu hardware info type as defined in the enum
  *                 iommu_hw_info_type.
+ * @out_capabilities: Output the generic iommu capability info type as defined
+ *                    in the enum iommu_hw_capabilities.
  * @__reserved: Must be 0
  *
  * Query an iommu type specific hardware information data from an iommu behind
@@ -453,6 +469,7 @@ struct iommu_hw_info {
 	__aligned_u64 data_uptr;
 	__u32 out_data_type;
 	__u32 __reserved;
+	__aligned_u64 out_capabilities;
 };
 #define IOMMU_GET_HW_INFO _IO(IOMMUFD_TYPE, IOMMUFD_CMD_GET_HW_INFO)