On 2019.07.09 10:12:33 +0100, 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.
>
> v2: Fiddle around with the flags and settle on using has-semaphores for
> the core bits so that we retain the ability to preempt our own
> semaphores.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
> Cc: Xiaolin Zhang <xiaolin.zhang@xxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
I've tried to run guest with this one for several benchmarks on SKL
and didn't observe hang. I think the hang met by Xiaolin might be caused
by other things that can be double checked later.
So for semaphore disable in vGPU case,
Acked-by: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
thanks!
> drivers/gpu/drm/i915/gt/intel_engine_cs.c | 4 ++--
> drivers/gpu/drm/i915/gt/intel_lrc.c | 24 +++++++++++++++++------
> drivers/gpu/drm/i915/gt/selftest_lrc.c | 6 ++++++
> 3 files changed, 26 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index 56310812da21..614ed8c488ef 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -825,6 +825,8 @@ 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
> @@ -852,8 +854,6 @@ 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 558a5850de3c..ef36f4b5e212 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -295,6 +295,9 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,
> {
> int last_prio;
>
> + if (!intel_engine_has_semaphores(engine))
> + return false;
> +
> /*
> * Check if the current priority hint merits a preemption attempt.
> *
> @@ -893,6 +896,9 @@ need_timeslice(struct intel_engine_cs *engine, const struct i915_request *rq)
> {
> int hint;
>
> + if (!intel_engine_has_semaphores(engine))
> + return false;
> +
> if (list_is_last(&rq->sched.link, &engine->active.requests))
> return false;
>
> @@ -2634,7 +2640,8 @@ 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_semaphores(request->engine))
> + cs = emit_preempt_busywait(request, cs);
>
> request->tail = intel_ring_offset(request, cs);
> assert_ring_tail_valid(request->ring, request->tail);
> @@ -2658,7 +2665,8 @@ 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_semaphores(request->engine))
> + cs = emit_preempt_busywait(request, cs);
>
> request->tail = intel_ring_offset(request, cs);
> assert_ring_tail_valid(request->ring, request->tail);
> @@ -2706,10 +2714,11 @@ 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)
> @@ -3399,7 +3408,6 @@ intel_execlists_create_virtual(struct i915_gem_context *ctx,
> ve->base.class = OTHER_CLASS;
> ve->base.uabi_class = I915_ENGINE_CLASS_INVALID;
> ve->base.instance = I915_ENGINE_CLASS_INVALID_VIRTUAL;
> - ve->base.flags = I915_ENGINE_IS_VIRTUAL;
>
> /*
> * The decision on whether to submit a request using semaphores
> @@ -3496,8 +3504,12 @@ 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;
> }
>
> + ve->base.flags |= I915_ENGINE_IS_VIRTUAL;
> +
> return &ve->context;
>
> err_put:
> diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> index fe4e15f9ba9d..a13f06ba984b 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> @@ -269,6 +269,9 @@ 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);
> @@ -354,6 +357,9 @@ static int live_busywait_preempt(void *arg)
> struct igt_live_test t;
> u32 *cs;
>
> + if (!intel_engine_has_preemption(engine))
> + continue;
> +
> if (!intel_engine_can_store_dword(engine))
> continue;
>
> --
> 2.22.0
>
--
Open Source Technology Center, Intel ltd.
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