Re: [PATCH v5 3/4] iommufd: Add IOMMU_GET_HW_INFO

On 2023/8/3 22:31, 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 need to be compatiable with the underlying IOMMU hardware. Hence,

compatible

userspace should know the IOMMU hardware capability before creating and configuring the stage-1 translation table to kernel.

This adds IOMMU_GET_HW_INFO ioctl to query the IOMMU hardware information (a.k.a capability) 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/main.c | 79 ++++++++++++++++++++++++++++++++++++ include/uapi/linux/iommufd.h | 36 ++++++++++++++++ 2 files changed, 115 insertions(+)

diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c index 94c498b8fdf6..a0302bcaa97c 100644 --- a/drivers/iommu/iommufd/main.c +++ b/drivers/iommu/iommufd/main.c @@ -17,6 +17,7 @@ #include <linux/bug.h> #include <uapi/linux/iommufd.h> #include <linux/iommufd.h> +#include "../iommu-priv.h" #include "io_pagetable.h" #include "iommufd_private.h" @@ -177,6 +178,81 @@ static int iommufd_destroy(struct iommufd_ucmd *ucmd) return 0; } +static int iommufd_zero_fill_user(void __user *ptr, size_t bytes) +{

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

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

• 	return -EFAULT;
  

• }
• return 0;

+}

+static int iommufd_get_hw_info(struct iommufd_ucmd *ucmd) +{

• u32 hw_info_type = IOMMU_HW_INFO_TYPE_NONE;
• struct iommu_hw_info *cmd = ucmd->cmd;
• unsigned int length = 0, data_len;
• struct iommufd_device *idev;
• const struct iommu_ops *ops;
• void __user *user_ptr;
• 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);
  

• user_ptr = u64_to_user_ptr(cmd->data_ptr);
• ops = dev_iommu_ops(idev->dev);
• if (!ops->hw_info)

• goto done;
  

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

• rc = PTR_ERR(data);
  

• goto out_err;
  

Can kfree() handle a ERR_PTR input? I am afraid not,

/** * kfree - free previously allocated memory * @object: pointer returned by kmalloc() or kmem_cache_alloc() * * If @object is NULL, no operation is performed. */ void kfree(const void *object) { struct folio *folio; struct slab *slab; struct kmem_cache *s;

trace_kfree(_RET_IP_, object);

if (unlikely(ZERO_OR_NULL_PTR(object))) return;

So, perhaps we should add

data = NULL;

before goto out_err;

?

• }
• /* driver has hw_info callback should have a unique hw_info_type */
• if (WARN_ON_ONCE(hw_info_type == IOMMU_HW_INFO_TYPE_NONE)) {

• rc = -ENODEV;
  

• goto out_err;
  

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

• rc = -EFAULT;
  

• goto out_err;
  

• }

+done:

• /*

• * 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(user_ptr + length,
  

• 			    cmd->data_len - length);
  

• if (rc)
  

• 	goto out_err;
  

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

+out_err:

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

+}

Others look good to me, feel free to add:

Reviewed-by: Lu Baolu baolu.lu@linux.intel.com

after above are addressed.

Best regards, baolu