[PATCH v2 2/4] iommu: Add new iommu op to get iommu hardware information

[Yi Liu <yi.l.liu@intel.com>]

From: Lu Baolu <baolu.lu@linux.intel.com>

Introduce a new iommu op to get the IOMMU hardware capabilities for
iommufd. This information will be used by any vIOMMU driver which is
owned by userspace.

This op chooses to make the special parameters opaque to the core. This
suits the current usage model where accessing any of the IOMMU device
special parameters does require a userspace driver that matches the kernel
driver. If a need for common parameters, implemented similarly by several
drivers, arises then there's room in the design to grow a generic parameter
set as well. No wrapper API is added as it is supposed to be used by
iommufd only.

Different IOMMU hardware would have different hardware information. So the
information reported differs as well. To let the external user understand
the difference. enum iommu_hw_info_type is defined. For the iommu drivers
that are capable to report hardware information, it should have a unique
iommu_hw_info_type. The iommu_hw_info_type is stored in struct iommu_ops.
For the driver oesn't report hardware information, just use
IOMMU_HW_INFO_TYPE_DEFAULT.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Co-developed-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
 include/linux/iommu.h        | 13 +++++++++++++
 include/uapi/linux/iommufd.h |  7 +++++++
 2 files changed, 20 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 7202d8ece343..3ef84ee359d2 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -15,6 +15,7 @@
 #include <linux/of.h>
 #include <linux/ioasid.h>
 #include <uapi/linux/iommu.h>
+#include <uapi/linux/iommufd.h>
 
 #define IOMMU_READ	(1 << 0)
 #define IOMMU_WRITE	(1 << 1)
@@ -222,6 +223,11 @@ struct iommu_iotlb_gather {
 /**
  * struct iommu_ops - iommu ops and capabilities
  * @capable: check capability
+ * @hw_info: IOMMU hardware information. The type of the returned data is
+ *           defined in include/uapi/linux/iommufd.h. The data buffer is
+ *           allocated in the IOMMU driver and the caller should free it
+ *           after use. Return the data buffer if success, or ERR_PTR on
+ *           failure.
  * @domain_alloc: allocate iommu domain
  * @probe_device: Add device to iommu driver handling
  * @release_device: Remove device from iommu driver handling
@@ -246,11 +252,17 @@ struct iommu_iotlb_gather {
  * @remove_dev_pasid: Remove any translation configurations of a specific
  *                    pasid, so that any DMA transactions with this pasid
  *                    will be blocked by the hardware.
+ * @driver_type: One of enum iommu_hw_info_type. This is used in the hw_info
+ *               reporting path. For the drivers that supports it, a unique
+ *               type should be defined. For the driver that does not support
+ *               it, this field is the IOMMU_HW_INFO_TYPE_DEFAULT that is 0.
+ *               Hence, such drivers do not need to care this field.
  * @pgsize_bitmap: bitmap of all possible supported page sizes
  * @owner: Driver module providing these ops
  */
 struct iommu_ops {
 	bool (*capable)(struct device *dev, enum iommu_cap);
+	void *(*hw_info)(struct device *dev, u32 *length);
 
 	/* Domain allocation and freeing by the iommu driver */
 	struct iommu_domain *(*domain_alloc)(unsigned iommu_domain_type);
@@ -279,6 +291,7 @@ struct iommu_ops {
 	void (*remove_dev_pasid)(struct device *dev, ioasid_t pasid);
 
 	const struct iommu_domain_ops *default_domain_ops;
+	enum iommu_hw_info_type driver_type;
 	unsigned long pgsize_bitmap;
 	struct module *owner;
 };
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index ccd36acad36a..955cbef640da 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -370,4 +370,11 @@ struct iommu_hwpt_alloc {
 	__u32 __reserved;
 };
 #define IOMMU_HWPT_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_HWPT_ALLOC)
+
+/**
+ * enum iommu_hw_info_type - IOMMU Hardware Info Types
+ */
+enum iommu_hw_info_type {
+	IOMMU_HW_INFO_TYPE_DEFAULT,
+};
 #endif
-- 
2.34.1