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

[Nicolin Chen]

On Mon, Sep 25, 2023 at 10:05:06AM -0300, Jason Gunthorpe wrote:
> 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);

OK. And always use sizeof(typeof(*from)) in the mcaro for the
current data_len, I assume?

Thanks
Nic