Re: [PATCH v3 3/4] iommufd: Add IOMMU_DEVICE_GET_HW_INFO

On 5/11/23 10:30 PM, Yi Liu wrote:

Under nested IOMMU translation, userspace owns the stage-1 translation table (e.g. the stage-1 page table of Intel VT-d or the context table of ARM SMMUv3, and etc.). Stage-1 translation tables are vendor specific, and needs to be compatiable with the underlying IOMMU hardware. Hence, userspace should know the IOMMU hardware capability before creating and configuring the stage-1 translation table to kernel.

This adds IOMMU_DEVICE_GET_HW_INFO to query the IOMMU hardware information for a given device. The returned data is vendor specific, userspace needs to decode it with the structure mapped by the @out_data_type field.

As only physical devices have IOMMU hardware, so this will return error if the given device is not a physical device.

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

---

drivers/iommu/iommufd/device.c | 72 +++++++++++++++++++++++++ drivers/iommu/iommufd/iommufd_private.h | 1 + drivers/iommu/iommufd/main.c | 3 ++ include/uapi/linux/iommufd.h | 37 +++++++++++++ 4 files changed, 113 insertions(+)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c index 051bd8e99858..bc99d092de8f 100644 --- a/drivers/iommu/iommufd/device.c +++ b/drivers/iommu/iommufd/device.c @@ -263,6 +263,78 @@ u32 iommufd_device_to_id(struct iommufd_device *idev) } EXPORT_SYMBOL_NS_GPL(iommufd_device_to_id, IOMMUFD); +static int iommufd_zero_fill_user(u64 ptr, int bytes) +{

• int index = 0;
• for (; index < bytes; index++) {

• if (put_user(0, (uint8_t __user *)u64_to_user_ptr(ptr + index)))
  

• 	return -EFAULT;
  

• }
• return 0;

+}

+int iommufd_device_get_hw_info(struct iommufd_ucmd *ucmd) +{

• struct iommu_hw_info *cmd = ucmd->cmd;
• unsigned int length = 0, data_len;
• struct iommufd_device *idev;
• const struct iommu_ops *ops;
• void *data = NULL;
• int rc = 0;
• 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->hw_info)

• goto done;
  

If the iommu driver doesn't provide a hw_info callback, it still returns success?

• /* driver has hw_info callback should have a unique hw_info_type */
• if (ops->hw_info_type == IOMMU_HW_INFO_TYPE_NONE) {

• pr_warn_ratelimited("iommu driver set an invalid type\n");
  

• rc = -ENODEV;
  

• goto out_err;
  

• }
• data = ops->hw_info(idev->dev, &data_len);
• if (IS_ERR(data)) {

• rc = PTR_ERR(data);
  

• goto out_err;
  

• }
• length = min(cmd->data_len, data_len);
• if (copy_to_user(u64_to_user_ptr(cmd->data_ptr), data, length)) {

• rc = -EFAULT;
  

• goto out_err;
  

• }
• /*

• * Zero the trailing bytes if the user buffer is bigger than the
  

• * data size kernel actually has.
  

• */
  

• if (length < cmd->data_len) {

• rc = iommufd_zero_fill_user(cmd->data_ptr + length,
  

• 			    cmd->data_len - length);
  

• if (rc)
  

• 	goto out_err;
  

• }

+done:

• cmd->data_len = length;
• cmd->out_data_type = ops->hw_info_type;
• rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));

+out_err:

• kfree(data);
• iommufd_put_object(&idev->obj);
• return rc;

+}

• static int iommufd_group_setup_msi(struct iommufd_group *igroup, struct iommufd_hw_pagetable *hwpt) {

Best regards, baolu