Introduce a helper function xe_userptr_populate_range to populate
a userptr range. This functions calls hmm_range_fault to read
CPU page tables and populate all pfns/pages of this virtual address
range. For system memory page, dma-mapping is performed
to get a dma-address which can be used later for GPU to access pages.

v1: Address review comments:
    separate a npage_in_range function (Matt)
    reparameterize function xe_userptr_populate_range function (Matt)
    move mmu_interval_read_begin() call into while loop (Thomas)
    s/mark_range_accessed/xe_mark_range_accessed (Thomas)
    use set_page_dirty_lock (vs set_page_dirty) (Thomas)
    move a few checking in xe_vma_userptr_pin_pages to hmm.c (Matt)
v2: Remove device private page support. Only support system
    pages for now. use dma-map-sg rather than dma-map-page (Matt/Thomas)
v3: Address review comments:
    Squash patch "drm/xe: Introduce a helper to free sg table" to current
    patch (Matt)
    start and end addresses are already page aligned (Matt)
    Do mmap_read_lock and mmap_read_unlock for hmm_range_fault incase of
    non system allocator call. (Matt)
    Drop kthread_use_mm and kthread_unuse_mm. (Matt)
    No need of kernel-doc for static functions.(Matt)
    Modify function names. (Matt)
    Free sgtable incase of dma_map_sgtable failure.(Matt)
    Modify loop for hmm_range_fault.(Matt)
v4: Remove the dummy function for xe_hmm_userptr_populate_range
    since CONFIG_HMM_MIRROR is needed. (Matt)
    Change variable names start/end to userptr_start/userptr_end.(Matt)
v5: Remove device private page support info from commit message. Since
    the patch doesn't support device page handling. (Thomas)
Signed-off-by: Oak Zeng <oak.zeng@intel.com>
Co-developed-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@intel.com>
Cc: Brian Welty <brian.welty@intel.com>
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240412095237.1048599-2-himal.prasad.ghimiray@intel.com