On Thu, May 23, 2024 at 01:07:24PM +0100, Tvrtko Ursulin wrote:
On 23/05/2024 12:19, Ville Syrjälä wrote:
On Thu, May 23, 2024 at 09:25:45AM +0100, Tvrtko Ursulin wrote:
On 22/05/2024 16:29, Vidya Srinivas wrote:
In some scenarios, the DPT object gets shrunk but the actual framebuffer did not and thus its still there on the DPT's vm->bound_list. Then it tries to rewrite the PTEs via a stale CPU mapping. This causes panic.
Suggested-by: Ville Syrjala ville.syrjala@linux.intel.com Cc: stable@vger.kernel.org Fixes: 0dc987b699ce ("drm/i915/display: Add smem fallback allocation for dpt") Signed-off-by: Vidya Srinivas vidya.srinivas@intel.com
drivers/gpu/drm/i915/gem/i915_gem_object.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h index 3560a062d287..e6b485fc54d4 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h @@ -284,7 +284,8 @@ bool i915_gem_object_has_iomem(const struct drm_i915_gem_object *obj); static inline bool i915_gem_object_is_shrinkable(const struct drm_i915_gem_object *obj) {
- return i915_gem_object_type_has(obj, I915_GEM_OBJECT_IS_SHRINKABLE);
- return i915_gem_object_type_has(obj, I915_GEM_OBJECT_IS_SHRINKABLE) &&
!obj->is_dpt;Is there a reason i915_gem_object_make_unshrinkable() cannot be used to mark the object at a suitable place?
Do you have a suitable place in mind? i915_gem_object_make_unshrinkable() contains some magic ingredients so doesn't look like it can be called willy nilly.
After it is created in intel_dpt_create?
I don't see that helper couldn't be called. It is called from madvise and tiling for instance without any apparent special considerations.
Did you actually read through i915_gem_object_make_unshrinkable()?
Also, there is no mention of this angle in the commit message so I assumed it wasn't considered. If it was, then it should have been mentioned why hacky solution was chosen instead...
I suppose.
Anyways, looks like I forgot to reply that I already pushed this with this extra comment added: /* TODO: make DPT shrinkable when it has no bound vmas */
... becuase IMO the special case is quite ugly and out of place. :(
Yeah, not the nicest. But there's already a is_dpt check in the i915_gem_object_is_framebuffer() right next door, so it's not *that* out of place.
Another option maybe could be to manually clear I915_GEM_OBJECT_IS_SHRINKABLE but I don't think that is supposed to be mutable, so might also have other issues. So a more proper solution with that approach would perhaps need some kind of gem_create_shmem_unshrinkable() function.
I don't remember from the top of my head how DPT magic works but if shrinker protection needs to be tied with VMAs there is also i915_make_make(un)shrinkable to try.
I presume you mistyped something there.