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Expose a debugfs control to override the page-size allocation mode used for user BOs. The interface allows switching between the default allocation policy, forced 2M, forced 1G, and mixed allocation modes at runtime. This provides a simple way to validate behavior and debug page-size-dependent allocation flows. The debugfs entry is built only when CONFIG_DRM_XE_DEBUG_PAGE_SIZE is enabled. v2 - update changelog to match mutex-based cur_index handling - reset cur_index when switching to mixed mode (sashiko) v3 - add CONFIG guard for page-size allocation debugfs support (Himal) - create debugfs entry under CONFIG_DRM_XE_DEBUG_PAGE_SIZE v4 - reorderd this patch with kconfig patch to ensure patch builds - Gurding this debug knob for only discrete graphics v5(Himal) - Guard all page size calls with CONFIG_DRM_XE_DEBUG_PAGE_SIZE v8(Himal) - For read/show used READ_ONCE instead lock - to match Reader used WRITE_ONCE under lock protection - change modes to string format to read/writer for debugfs v9(Himal) - Add an OOB guard for mode in page_size_alloc_mode_show(). This check makes the function display "unknown" if mode has been maliciously altered by KMD, preventing out-of-bounds access. Under normal operation, values set through debugfs are validated, so OOB values should not occur. - simplify mode-to-string lookup using page_size_alloc_mode_names[] - use sysfs_match_string() to parse page_size_alloc_mode writes Signed-off-by: Nareshkumar Gollakoti <naresh.kumar.g@intel.com> Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com> Link: https://patch.msgid.link/20260729121843.1255891-3-naresh.kumar.g@intel.com Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>