[Intel-gfx] [PATCH v5] drm/i915/execlists: Disable preemption under GVT

[Zhang, Xiaolin]

On 06/24/2019 05:48 PM, Chris Wilson wrote:
> Preempt-to-busy uses a GPU semaphore to enforce an idle-barrier across
> preemption, but mediated gvt does not fully support semaphores.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/gt/intel_engine_cs.c |  4 ++--
>  drivers/gpu/drm/i915/gt/intel_lrc.c       | 21 ++++++++++++++++-----
>  drivers/gpu/drm/i915/gt/selftest_lrc.c    |  3 +++
>  3 files changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index 4961f74fd902..d6fbc47727c1 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -830,6 +830,8 @@ int intel_engine_init_common(struct intel_engine_cs *engine)
>  	struct drm_i915_private *i915 = engine->i915;
>  	int ret;
>  
> +	engine->set_default_submission(engine);
> +
>  	/* We may need to do things with the shrinker which
>  	 * require us to immediately switch back to the default
>  	 * context. This can cause a problem as pinning the
> @@ -857,8 +859,6 @@ int intel_engine_init_common(struct intel_engine_cs *engine)
>  
>  	engine->emit_fini_breadcrumb_dw = ret;
>  
> -	engine->set_default_submission(engine);
> -
>  	return 0;
>  
>  err_unpin:
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index c8a0c9b32764..8017efb36f7b 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -294,6 +294,9 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,
>  {
>  	int last_prio;
>  
> +	if (!intel_engine_has_preemption(engine))
> +		return false;
> +
>  	/*
>  	 * Check if the current priority hint merits a preemption attempt.
>  	 *
> @@ -890,6 +893,9 @@ need_timeslice(struct intel_engine_cs *engine, const struct i915_request *rq)
>  {
>  	int hint;
>  
> +	if (!intel_engine_has_preemption(engine))
> +		return false;
> +
>  	if (list_is_last(&rq->sched.link, &engine->active.requests))
>  		return false;
>  
> @@ -2600,7 +2606,8 @@ static u32 *gen8_emit_fini_breadcrumb(struct i915_request *request, u32 *cs)
>  	*cs++ = MI_USER_INTERRUPT;
>  
>  	*cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
> -	cs = emit_preempt_busywait(request, cs);
> +	if (intel_engine_has_preemption(request->engine))
> +		cs = emit_preempt_busywait(request, cs);
>  
>  	request->tail = intel_ring_offset(request, cs);
>  	assert_ring_tail_valid(request->ring, request->tail);
> @@ -2624,7 +2631,8 @@ static u32 *gen8_emit_fini_breadcrumb_rcs(struct i915_request *request, u32 *cs)
>  	*cs++ = MI_USER_INTERRUPT;
>  
>  	*cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
> -	cs = emit_preempt_busywait(request, cs);
> +	if (intel_engine_has_preemption(request->engine))
> +		cs = emit_preempt_busywait(request, cs);
>  
>  	request->tail = intel_ring_offset(request, cs);
>  	assert_ring_tail_valid(request->ring, request->tail);
> @@ -2672,10 +2680,11 @@ void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
>  	engine->unpark = NULL;
>  
>  	engine->flags |= I915_ENGINE_SUPPORTS_STATS;
> -	if (!intel_vgpu_active(engine->i915))
> +	if (!intel_vgpu_active(engine->i915)) {
>  		engine->flags |= I915_ENGINE_HAS_SEMAPHORES;
> -	if (HAS_LOGICAL_RING_PREEMPTION(engine->i915))
> -		engine->flags |= I915_ENGINE_HAS_PREEMPTION;
> +		if (HAS_LOGICAL_RING_PREEMPTION(engine->i915))
> +			engine->flags |= I915_ENGINE_HAS_PREEMPTION;
> +	}
>  }
>  
>  static void execlists_destroy(struct intel_engine_cs *engine)
> @@ -3463,6 +3472,8 @@ intel_execlists_create_virtual(struct i915_gem_context *ctx,
>  		ve->base.emit_fini_breadcrumb = sibling->emit_fini_breadcrumb;
>  		ve->base.emit_fini_breadcrumb_dw =
>  			sibling->emit_fini_breadcrumb_dw;
> +
> +		ve->base.flags = sibling->flags;
>  	}
>  
>  	return &ve->context;
> diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> index 0c97f953e908..b99b589a6c81 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> @@ -270,6 +270,9 @@ static int live_timeslice_preempt(void *arg)
>  		enum intel_engine_id id;
>  
>  		for_each_engine(engine, i915, id) {
> +			if (!intel_engine_has_preemption(engine))
> +				continue;
> +
>  			memset(vaddr, 0, PAGE_SIZE);
>  
>  			err = slice_semaphore_queue(engine, vma, count);

Tested-by:  Xiaolin Zhang <xiaolin.zhang at intel.com>

with this patch, linux guest can boot up successfully with sanity test passed. But it is easy to get the GPU hang when running "vblank_mode=0 glxgears" in guest for about 4-5 mins. I believe this GPU hang is not caused by this patch, so it could be OK for next step.