RE: [PATCH v2 3/4] iommufd: Add IOMMU_DEVICE_GET_HW_INFO

From: Liu, Yi L yi.l.liu@intel.com Sent: Thursday, March 9, 2023 3:54 PM

+int iommufd_device_get_hw_info(struct iommufd_ucmd *ucmd) +{

• struct iommu_hw_info *cmd = ucmd->cmd;
• struct iommufd_device *idev;
• const struct iommu_ops *ops;
• void *data;
• unsigned int length, data_len;
• int rc;
• if (cmd->flags || cmd->__reserved || !cmd->data_len)

• return -EOPNOTSUPP;
  

• idev = iommufd_get_device(ucmd, cmd->dev_id);
• if (IS_ERR(idev))

• return PTR_ERR(idev);
  

• ops = dev_iommu_ops(idev->dev);
• if (!ops || !ops->hw_info) {

• rc = -EOPNOTSUPP;
  

• goto out_put;
  

• }
• /* driver has hw_info callback should have a unique driver_type */
• if (WARN_ON(ops->driver_type ==

IOMMU_HW_INFO_TYPE_DEFAULT)) {

• rc = -EOPNOTSUPP;
  

• goto out_put;
  

• }

ok, here is where the check is done.

• data = ops->hw_info(idev->dev, &data_len);

if we directly return type in @hw_info, this becomes:

data = ops->hw_info(idev->dev, &data_len, &driver_type);

+/**

• • struct iommu_hw_info - ioctl(IOMMU_DEVICE_GET_HW_INFO)
• • @size: sizeof(struct iommu_hw_info)
• • @flags: Must be 0
• • @dev_id: The device being attached to the iommufd

"The device bound to the iommufd"

• • @data_len: Input the length of the user buffer in bytes. Output the

• •        length of data filled to the user buffer.
    

s/to/in/

• • @data_ptr: Pointer to the type specific structure

"Pointer to the user buffer"

• • @out_data_type: Output the iommu hardware info type, it is one of

• •             enum iommu_hw_info_type.
    

s/it is one of/as defined by/

• • @__reserved: Must be 0
• • Query the hardware iommu information for given device which has been
• • bound to iommufd. @data_len is the size of the buffer which captures
• • iommu type specific data and the data will be filled. Trailing bytes
• • are zeroed if the user buffer is larger than the data kernel has.
• • The type specific data would be used to sync capability between the
• • vIOMMU and the hardware IOMMU. e.g. nested translation requires to

s/vIOMMU/virtual IOMMU/

• • check the hardware IOMMU capability, since a stage-1 translation table
• • is owned by user but used by hardware IOMMU.

"check ... capability so guest stage-1 page table uses a format compatible to the hardware IOMMU"

• • The @out_data_type will be filled if the ioctl succeeds. It would
• • be used to decode the data filled in the buffer pointed by @data_ptr.
• • This is only available for the physical devices bound to iommufd as
• • only physical devices can have hardware IOMMU.

not required. User doesn't know whether it's physical or emulated device.