Now that Chris Wilson demonstrated that the key for stability on early gen 2 is to simple _never_ exchange the physical backing storage of batch buffers I've tried a stab at a kernel solution. Doesn't look too nefarious imho, now that I don't try to be too clever for my own good any more. v2: After discussing the various techniques, we've decided to always blit batches on the suspect devices, but allow userspace to opt out of the kernel workaround assume full responsibility for providing coherent batches. The principal reason is that avoiding the blit does improve performance in a few key microbenchmarks and also in cairo-trace replays.
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| @@ -307,6 +307,7 @@ typedef struct drm_i915_irq_wait { · 306 unmodified lines | |||
| 307 | #define I915_PARAM_HAS_PRIME_VMAP_FLUSH 21 | 307 | #define I915_PARAM_HAS_PRIME_VMAP_FLUSH 21 |
| 308 | #define I915_PARAM_RSVD_FOR_FUTURE_USE 22 | 308 | #define I915_PARAM_RSVD_FOR_FUTURE_USE 22 |
| 309 | #define I915_PARAM_HAS_SECURE_BATCHES 23 | 309 | #define I915_PARAM_HAS_SECURE_BATCHES 23 |
| 310 | #define I915_PARAM_HAS_PINNED_BATCHES 24 | ||
| 310 | 311 | ||
| 311 | typedef struct drm_i915_getparam { | 312 | typedef struct drm_i915_getparam { |
| 312 | int param; | 313 | int param; |
| @@ -677,6 +678,15 @@ struct drm_i915_gem_execbuffer2 { · 364 unmodified lines | |||
| 677 | */ | 678 | */ |
| 678 | #define I915_EXEC_SECURE (1<<9) | 679 | #define I915_EXEC_SECURE (1<<9) |
| 679 | 680 | ||
| 681 | /** Inform the kernel that the batch is and will always be pinned. This | ||
| 682 | * negates the requirement for a workaround to be performed to avoid | ||
| 683 | * an incoherent CS (such as can be found on 830/845). If this flag is | ||
| 684 | * not passed, the kernel will endeavour to make sure the batch is | ||
| 685 | * coherent with the CS before execution. If this flag is passed, | ||
| 686 | * userspace assumes the responsibility for ensuring the same. | ||
| 687 | */ | ||
| 688 | #define I915_EXEC_IS_PINNED (1<<10) | ||
| 689 | |||
| 680 | #define I915_EXEC_CONTEXT_ID_MASK (0xffffffff) | 690 | #define I915_EXEC_CONTEXT_ID_MASK (0xffffffff) |
| 681 | #define i915_execbuffer2_set_context_id(eb2, context) \ | 691 | #define i915_execbuffer2_set_context_id(eb2, context) \ |
| 682 | (eb2).rsvd1 = context & I915_EXEC_CONTEXT_ID_MASK | 692 | (eb2).rsvd1 = context & I915_EXEC_CONTEXT_ID_MASK |