On 15/02/2023 01:56, Ceraolo Spurio, Daniele wrote:
On 2/14/2023 3:48 PM, John.C.Harrison@xxxxxxxxx wrote:
From: John Harrison <John.C.Harrison@xxxxxxxxx>
Direction from hardware is that stolen memory should never be used for
ring buffer allocations. There are too many caching pitfalls due to the
way stolen memory accesses are routed. So it is safest to just not use
it.
I'm wondering if this applies to machines in ringbuffer mode as well, as
some of the caching stuff that according to the HW team may not work
properly with stolen mem accesses from the CS (mocs, ppat) came with
gen8/gen9.
Maybe limit this change to gen8+, to avoid changing the behavior for
very old platforms?
If Gen8+ can have bugs due this then:
Fixes: c58b735fc762 ("drm/i915: Allocate rings from stolen")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.9+
Or even before:
Fixes: ebc052e0c65f ("drm/i915: Allocate ringbuffers from stolen memory")
Cc: <stable@xxxxxxxxxxxxxxx> # v3.9+
Hm lets see when BDW when out of force probe:
Fixes: babb1903511f ("drm/i915/bdw: remove preliminary_hw_support flag from BDW")
Cc: <stable@xxxxxxxxxxxxxxx> # v3.14+
Depends also how the problem statement interacts with LLC. If !LLC platforms are okay then the first one from the above list is enough.
Because
Regards,
Tvrtko
Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_ring.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_ring.c
b/drivers/gpu/drm/i915/gt/intel_ring.c
index 15ec64d881c44..d1a47e1ae6452 100644
--- a/drivers/gpu/drm/i915/gt/intel_ring.c
+++ b/drivers/gpu/drm/i915/gt/intel_ring.c
@@ -116,8 +116,6 @@ static struct i915_vma *create_ring_vma(struct
i915_ggtt *ggtt, int size)
obj = i915_gem_object_create_lmem(i915, size,
I915_BO_ALLOC_VOLATILE |
I915_BO_ALLOC_PM_VOLATILE);
- if (IS_ERR(obj) && i915_ggtt_has_aperture(ggtt))
- obj = i915_gem_object_create_stolen(i915, size);
There is code in ring_pin/unpin() that only applies to rings in stolen
memory, so you need to remove that as well if you drop stolen for rings
on all platforms.
Daniele
if (IS_ERR(obj))
obj = i915_gem_object_create_internal(i915, size);
if (IS_ERR(obj))
