drm/xe/reg_sr: Apply limit to register whitelisting

If RING_MAX_NONPRIV_SLOTS denotes the maximum number of whitelisting
slots, then it makes sense to refuse going above it.

v2:
  - Use xe_gt_err() instead of drm_err() for more detailed info in the
    error message. (Matt)

Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20230609143815.302540-3-gustavo.sousa@intel.comSigned-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_reg_sr.c

@@ -235,6 +235,13 @@ void xe_reg_sr_apply_whitelist(struct xe_hw_engine *hwe)
 
 	p = drm_debug_printer(KBUILD_MODNAME);
 	xa_for_each(&sr->xa, reg, entry) {
+		if (slot == RING_MAX_NONPRIV_SLOTS) {
+			xe_gt_err(gt,
+				  "hwe %s: maximum register whitelist slots (%d) reached, refusing to add more\n",
+				  hwe->name, RING_MAX_NONPRIV_SLOTS);
+			break;
+		}
+
 		xe_reg_whitelist_print_entry(&p, 0, reg, entry);
 		xe_mmio_write32(gt, RING_FORCE_TO_NONPRIV(mmio_base, slot),
 				reg | entry->set_bits);