[REGRESSION][BISECTED] drm/i915: GPU HANGs on v6.12.20+

TLDR: on kernels v6.12.x i915_gem_mmap_gtt_version() should return 4

Hi,

This patch shipped with v6.12.20 introduces GPU HANGs on Intel UHD Graphics 620 
(8gen igpu)

index 21274aa9bdddc1..c3dabb85796052 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -164,6 +164,9 @@ static unsigned int tile_row_pages(const struct drm_i915_gem
_object *obj)
  * 4 - Support multiple fault handlers per object depending on object's
  *     backing storage (a.k.a. MMAP_OFFSET).
  *
+ * 5 - Support multiple partial mmaps(mmap part of BO + unmap a offset, multipl
e
+ *     times with different size and offset).
+ *
  * Restrictions:
  *
  *  * snoopable objects cannot be accessed via the GTT. It can cause machine
@@ -191,7 +194,7 @@ static unsigned int tile_row_pages(const struct drm_i915_gem
_object *obj)
  */
 int i915_gem_mmap_gtt_version(void)
 {
-   return 4;
+   return 5;
 }

kernel: i915 0000:00:02.0: [drm] Resetting rcs0 for preemption time out
kernel: i915 0000:00:02.0: [drm] aces[2257] context reset due to GPU hang
kernel: i915 0000:00:02.0: [drm] GPU HANG: ecode 9:1:e757fefe, in aces [2257]
kernel: i915 0000:00:02.0: [drm] Resetting rcs0 for preemption time out
kernel: i915 0000:00:02.0: [drm] aces[2257] context reset due to GPU hang
kernel: i915 0000:00:02.0: [drm] GPU HANG: ecode 9:1:e757fefe, in aces [2257]
kernel: BUG: unable to handle page fault for address: 0000000078280000
kernel: #PF: supervisor read access in kernel mode
kernel: #PF: error_code(0x0000) - not-present page
kernel: PGD 1462e9067 P4D 1462e9067 PUD 0 
kernel: Oops: Oops: 0000 [#1] PREEMPT SMP

GPU hangs if i915_gem_mmap_gtt_version() returns 5. If set to return 4(as it was
 in v6.12.19) no HANG occur. This happens on v6.12.20+ kernels ONLY, v6.6.x, v6.
18.x, v7.1.3 and v6.12.19 are unaffected.

The actual commit introducing this is bfef148f3680e6b9d28e7fca46d9520f80c5e50e, 
but it doesn't seem to affect any other kernel tree.

#regzbot introduced: v6.12.19..v6.12.20