drm/xe/vm: Subclass userptr vmas

The construct allocating only parts of the vma structure when
the userptr part is not needed is very fragile. A developer could
add additional fields below the userptr part, and the code could
easily attempt to access the userptr part even if its not persent.

So introduce xe_userptr_vma which subclasses struct xe_vma the
proper way, and accordingly modify a couple of interfaces.
This should also help if adding userptr helpers to drm_gpuvm.

v2:
- Fix documentation of to_userptr_vma() (Matthew Brost)
- Fix allocation and freeing of vmas to clearer distinguish
  between the types.

Closes: https://lore.kernel.org/intel-xe/[email protected]/T/#u
Fixes: a4cc60a55fd9 ("drm/xe: Only alloc userptr part of xe_vma for userptrs")
Cc: Rodrigo Vivi <[email protected]>
Cc: Matthew Brost <[email protected]>
Cc: Lucas De Marchi <[email protected]>
Signed-off-by: Thomas Hellström <[email protected]>
Reviewed-by: Matthew Brost <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit 5bd24e78829ad569fa1c3ce9a05b59bb97b91f3d)
Signed-off-by: Thomas Hellström <[email protected]>

0 files changed, 0 insertions, 0 deletions