drm/xe: Restrict huge PTEs to 1GiB

Add a define for the highest level for which we can encode a huge PTE,
and use it for page-table building. Also update an assert that checks that
we don't try to encode for larger sizes.
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Brian Welty <brian.welty@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231209151843.7903-2-thomas.hellstrom@linux.intel.comSigned-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_pt.c

@@ -430,6 +430,9 @@ static bool xe_pt_hugepte_possible(u64 addr, u64 next, unsigned int level,
 {
 	u64 size, dma;
 
+	if (level > MAX_HUGEPTE_LEVEL)
+		return false;
+
 	/* Does the virtual range requested cover a huge pte? */
 	if (!xe_pt_covers(addr, next, level, &xe_walk->base))
 		return false;

drivers/gpu/drm/xe/xe_pt.h

@@ -18,6 +18,9 @@ struct xe_tile;
 struct xe_vm;
 struct xe_vma;
 
+/* Largest huge pte is currently 1GiB. May become device dependent. */
+#define MAX_HUGEPTE_LEVEL 2
+
 #define xe_pt_write(xe, map, idx, data) \
 	xe_map_wr(xe, map, (idx) * sizeof(u64), u64, data)
 

drivers/gpu/drm/xe/xe_vm.c

@@ -1258,7 +1258,7 @@ static u64 pte_encode_pat_index(struct xe_device *xe, u16 pat_index,
 
 static u64 pte_encode_ps(u32 pt_level)
 {
-	XE_WARN_ON(pt_level > 2);
+	XE_WARN_ON(pt_level > MAX_HUGEPTE_LEVEL);
 
 	if (pt_level == 1)
 		return XE_PDE_PS_2M;