Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for domain_alloc_user op

[Jason Gunthorpe]

On Thu, Sep 21, 2023 at 01:58:19PM -0700, Nicolin Chen wrote:

> Perhaps we could put all min_len defines in uAPI header, like:
> include/uapi/linux/gfs2_ondisk.h:442:#define LH_V1_SIZE (offsetofend(struct gfs2_log_header, lh_hash))
> In this way, drivers won't need to deal with that nor have risks
> of breaking ABI by changing a min_len.

I don't think we need constants, just be sure that every call to 
iommu_copy_user_data() has an offsetof() as the last parameter.

Indeed perhaps you should put it in a macro and force this to happen eg:

 #define iommu_copy_user_data(user_data, from, min_size_member) \
  __iommu_copy_user_data(user_data, from, offsetofend(typeof(*from), min_size_member))

 iommu_copy_user_data(user_data, &data, iotlb);

Jason