On Fri, Apr 08, 2016 at 02:54:56PM +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko@xxxxxxxxxxx>
>
> In GuC mode submitting requests is only putting them into the
> GuC queue with the actual submission to hardware following at
> some future point. This makes the per engine last context
> tracking insufficient for closing the premature context
> unpin race.
>
> Instead we need to make requests track and pin the previous
> context on the same engine, and only unpin them when they
> themselves are retired. This will ensure contexts remain pinned
> in all cases until the are fully saved by the GPU.
>
> v2: Only track contexts.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko@xxxxxxxxxxx>
> Cc: Alex Dai <yu.dai@xxxxxxxxx>
> Cc: Dave Gordon <david.s.gordon@xxxxxxxxx>
> Cc: Nick Hoath <nicholas.hoath@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 4 +++-
> drivers/gpu/drm/i915/i915_gem.c | 5 +++++
> drivers/gpu/drm/i915/intel_lrc.c | 17 +++++++++++++++++
> 3 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index fa199b7e51b5..216b2297ae3e 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2283,6 +2283,9 @@ struct drm_i915_gem_request {
> struct intel_context *ctx;
> struct intel_ringbuffer *ringbuf;
>
> + /** Context preceding this one on the same engine. Can be NULL. */
> + struct intel_context *prev_ctx;
> +
> /** Batch buffer related to this request if any (used for
> error state dump only) */
> struct drm_i915_gem_object *batch_obj;
> @@ -2318,7 +2321,6 @@ struct drm_i915_gem_request {
>
> /** Execlists no. of times this request has been sent to the ELSP */
> int elsp_submitted;
> -
> };
>
> struct drm_i915_gem_request * __must_check
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index c1df696f9002..118911ce7231 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1445,6 +1445,11 @@ static void i915_gem_request_retire(struct drm_i915_gem_request *request)
> */
> request->ringbuf->last_retired_head = request->postfix;
>
> + if (request->prev_ctx) {
> + intel_lr_context_unpin(request->prev_ctx, request->engine);
> + request->prev_ctx = NULL;
> + }
> +
> __i915_gem_request_release(request);
> }
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 31445aa3429b..3d08dac0a9b0 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -798,6 +798,23 @@ intel_logical_ring_advance_and_submit(struct drm_i915_gem_request *request)
> if (intel_engine_stopped(engine))
> return 0;
>
> + /*
> + * Pin the previous context on this engine to ensure it is not
> + * prematurely unpinned in GuC mode.
> + * Previous context will be unpinned when this request is retired,
> + * ensuring the GPU has switched out from the previous context and into
> + * a new context at that point.
> + */
> + if (engine->last_context) {
> + if (engine->last_context != request->i915->kernel_context) {
> + intel_lr_context_pin(engine->last_context, engine);
> + request->prev_ctx = engine->last_context;
> + }
> + }
> +
> + /*
> + * Track and pin the last context submitted on an engine.
> + */
> if (engine->last_context != request->ctx) {
> if (engine->last_context)
> intel_lr_context_unpin(engine->last_context, engine);
We can use pinned_context to reduce the code complexity, not make it
worse.
If you first apply the execlists default context fix, adding
pinned_context is a reduction is code.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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