drm/xe: Fix page reclaim entry handling for large pages

drm/xe: Fix page reclaim entry handling for large pages

For 64KB pages, XE_PTE_PS64 is defined for all consecutive 4KB pages and
are all considered leaf nodes, so existing check was falsely adding
multiple 64KB pages to PRL.

For larger entries such as 2MB PDE, the check for pte->base.children is
insufficient since this array is always  defined for page directory,
level 1 and above, so perform a check on the entry itself pointing to
the correct page.

For unmaps, if the range is properly covered by the page full directory,
page walker may finish without walking to the leaf nodes.

For example, a 1G range can be fully covered by 512 2MB pages if
alignment allows. In this case, the page walker will walk until
it reaches this corresponding directory which can correlate to the 1GB
range. Page walker will simply complete its walk and the individual 2MB
PDE leaves won't get accessed.

In this case, PRL invalidation is also required, so add a check to see if
pt entry cover the entire range since the walker will complete the walk.

There are possible race conditions that will cause driver to read a pte
that hasn't been written to yet. The 2 scenarios are:
 - Another issued TLB invalidation such as from userptr or MMU notifier.
 - Dependencies on original bind that has yet to be executed with an
   unbind on that job.

The expectation is these race conditions are likely rare cases so simply
perform a fallback to full PPC flush invalidation instead.

v2:
 - Reword commit and updated zero-pte handling. (Matthew B)

v3:
 - Rework if statement for abort case with additional comments. (Matthew B)

Fixes: b912138df299 ("drm/xe: Create page reclaim list on unbind")
Signed-off-by: Brian Nguyen <brian3.nguyen@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260107010447.4125005-9-brian3.nguyen@intel.com