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

On 2023/3/9 15:53, 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 | 74 +++++++++++++++++++++++++ drivers/iommu/iommufd/iommufd_private.h | 1 + drivers/iommu/iommufd/main.c | 3 + include/uapi/linux/iommufd.h | 40 +++++++++++++ 4 files changed, 118 insertions(+)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c index c10e02f6a0be..6948539488a5 100644 --- a/drivers/iommu/iommufd/device.c +++ b/drivers/iommu/iommufd/device.c @@ -257,6 +257,80 @@ struct iommufd_ctx *iommufd_device_to_ictx(struct iommufd_device *idev) } EXPORT_SYMBOL_NS_GPL(iommufd_device_to_ictx, 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 *)(ptr + index)))
  

• 	return -EFAULT;
  

• }
• return 0;

+}

+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;

Reverse christmas tree order for declarations.

• 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) {

dev_iommu_ops() will never return a NULL.

Need below check

dev->iommu && dev->iommu->iommu_dev

before dev_iommu_ops(). Perhaps something like below?

if (!dev->iommu || !dev->iommu->iommu_dev) return -EINVAL;

ops = dev_iommu_ops(idev->dev); if (!ops->hw_info) return -ENODEV;

• 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)) {

If so, perhaps IOMMU_HW_INFO_TYPE_INVALID is more readable?

I'm not sure if a calltrace is really necessary here. If not, perhaps,

if (ops->driver_type == IOMMU_HW_INFO_TYPE_DEFAULT) { pr_warn_ratelimited("iommu driver set an invalid type\n"); rc = -ENODEV; goto out_put; }

• rc = -EOPNOTSUPP;
  

• goto out_put;
  

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

• rc = PTR_ERR(data);
  

• goto out_put;
  

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

• rc = -EFAULT;
  

• goto out_free_data;
  

• }
• /*

• * 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_free_data;
  

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

+out_free_data:

• kfree(data);

+out_put:

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

+}

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

diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h index b18f843ad6a4..05b5ad66f716 100644 --- a/drivers/iommu/iommufd/iommufd_private.h +++ b/drivers/iommu/iommufd/iommufd_private.h @@ -307,6 +307,7 @@ iommufd_get_device(struct iommufd_ucmd *ucmd, u32 id) } void iommufd_device_destroy(struct iommufd_object *obj); +int iommufd_device_get_hw_info(struct iommufd_ucmd *ucmd); struct iommufd_access { struct iommufd_object obj; diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c index 694da191e4b1..f079c0bda46b 100644 --- a/drivers/iommu/iommufd/main.c +++ b/drivers/iommu/iommufd/main.c @@ -262,6 +262,7 @@ static int iommufd_option(struct iommufd_ucmd *ucmd) union ucmd_buffer { struct iommu_destroy destroy; struct iommu_hwpt_alloc hwpt;

• struct iommu_hw_info info; struct iommu_ioas_alloc alloc; struct iommu_ioas_allow_iovas allow_iovas; struct iommu_ioas_copy ioas_copy;

@@ -295,6 +296,8 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = { IOCTL_OP(IOMMU_DESTROY, iommufd_destroy, struct iommu_destroy, id), IOCTL_OP(IOMMU_HWPT_ALLOC, iommufd_hwpt_alloc, struct iommu_hwpt_alloc, __reserved),

• IOCTL_OP(IOMMU_DEVICE_GET_HW_INFO, iommufd_device_get_hw_info,

•  struct iommu_hw_info, __reserved),
  

  IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl, struct iommu_ioas_alloc, out_ioas_id), IOCTL_OP(IOMMU_IOAS_ALLOW_IOVAS, iommufd_ioas_allow_iovas,

diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h index 955cbef640da..4ac525897b82 100644 --- a/include/uapi/linux/iommufd.h +++ b/include/uapi/linux/iommufd.h @@ -46,6 +46,7 @@ enum { IOMMUFD_CMD_OPTION, IOMMUFD_CMD_VFIO_IOAS, IOMMUFD_CMD_HWPT_ALLOC,

• IOMMUFD_CMD_DEVICE_GET_HW_INFO, };

/** @@ -377,4 +378,43 @@ struct iommu_hwpt_alloc { enum iommu_hw_info_type { IOMMU_HW_INFO_TYPE_DEFAULT, };

+/**

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

• •        length of data filled to the user buffer.
    

• • @data_ptr: Pointer to the type specific structure
• • @out_data_type: Output the iommu hardware info type, it is one of

• •             enum iommu_hw_info_type.
    

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

+struct iommu_hw_info {

• __u32 size;
• __u32 flags;
• __u32 dev_id;
• __u32 data_len;
• __aligned_u64 data_ptr;
• __u32 out_data_type;
• __u32 __reserved;

+}; +#define IOMMU_DEVICE_GET_HW_INFO _IO(IOMMUFD_TYPE, IOMMUFD_CMD_DEVICE_GET_HW_INFO) #endif

Other look good to me.

Best regards, baolu