On 23/05/2024 13:24, Ville Syrjälä wrote:
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@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 0dc987b699ce ("drm/i915/display: Add smem fallback allocation for dpt")
Signed-off-by: Vidya Srinivas <vidya.srinivas@xxxxxxxxx>
---
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()?
Briefly, and also looked around how it is used. I don't immediately
understand which part concerns you and it is also quite possible I am
missing something.
But see for example how it is used in intel_context.c+intel_lrc.c to
protect the context state object from the shrinker while it is in use by
the GPU. It does not appear any black magic is required.
Question also is does that kind of lifetime aligns with the DPT use case.
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.
I also see who added that one! ;)
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.
Oops - i915_vma_make_(un)shrinkable.
Anyway, I think it is worth giving it a try if the DPT lifetimes makes
it possible.
Regards,
Tvrtko
