Re: [PATCH v2] x86/sgx: use vm_flags_t for vm_prot_bits

On Thu, 2026-01-22 at 21:36 +0800, Wentong Tian wrote:
> The vm_flags_t type is the dedicated type for virtual memory flags.
> Architecture and driver code should use this type instead of assuming
> vm_flags is an unsigned long, as the underlying type may change in the
> future.
> 
> This follows the cleanup in commit d75fa3c94750 ("mm: update
> architecture and driver code to use vm_flags_t") by converting the
> remaining vm_prot_bits usage in SGX code. Also, update the vm_max_prot_bits
> type in struct sgx_encl_page to vm_flags_t for consistency.
> 
> No functional change intended.
> 
> Signed-off-by: Wentong Tian <[email protected]>
> ---
> v2:
>  - Also convert the type of vm_max_prot_bits in struct sgx_encl_page
>    to vm_flags_t, as suggested.

Hmm I was actually just pointing out, but not suggesting, since I am not
sure (honestly).

Back to technical:

Gcc doc says:

  A structure field declaration with an integer type can specify the 
  number of bits the field should occupy. We call that a bit field.

With vm_flags_t I think "theoretically" it could stop being integer type
someday.  But I guess the advantage is when someone does that that can
trigger build error here (so that we can be aware) which perhaps isn't a
bad thing?