Re: [PATCH 03/26] drm/i915/guc: Take engine PM when a context is pinned with GuC submission

[Matthew Brost <matthew.brost@xxxxxxxxx>]

On Wed, Oct 06, 2021 at 08:45:42PM -0700, John Harrison wrote:
> On 10/4/2021 15:06, Matthew Brost wrote:
> > Taking a PM reference to prevent intel_gt_wait_for_idle from short
> > circuiting while a scheduling of user context could be enabled.
> I'm not sure what 'while a scheduling of user context could be enabled'
> means.
>

Not really sure how this isn't clear.

It means if a user context has scheduling enabled this function cannot
short circuit returning idle.

Matt
 
> John.
> 
> > Returning GT idle when it is not can cause all sorts of issues
> > throughout the stack.
> > 
> > v2:
> >   (Daniel Vetter)
> >    - Add might_lock annotations to pin / unpin function
> > v3:
> >   (CI)
> >    - Drop intel_engine_pm_might_put from unpin path as an async put is
> >      used
> > v4:
> >   (John Harrison)
> >    - Make intel_engine_pm_might_get/put work with GuC virtual engines
> >    - Update commit message
> > 
> > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> > ---
> >   drivers/gpu/drm/i915/gt/intel_context.c       |  2 ++
> >   drivers/gpu/drm/i915/gt/intel_engine_pm.h     | 32 +++++++++++++++++
> >   drivers/gpu/drm/i915/gt/intel_gt_pm.h         | 10 ++++++
> >   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 36 +++++++++++++++++--
> >   drivers/gpu/drm/i915/intel_wakeref.h          | 12 +++++++
> >   5 files changed, 89 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> > index 1076066f41e0..f601323b939f 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_context.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_context.c
> > @@ -240,6 +240,8 @@ int __intel_context_do_pin_ww(struct intel_context *ce,
> >   	if (err)
> >   		goto err_post_unpin;
> > +	intel_engine_pm_might_get(ce->engine);
> > +
> >   	if (unlikely(intel_context_is_closed(ce))) {
> >   		err = -ENOENT;
> >   		goto err_unlock;
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.h b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> > index 6fdeae668e6e..d68675925b79 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> > @@ -6,9 +6,11 @@
> >   #ifndef INTEL_ENGINE_PM_H
> >   #define INTEL_ENGINE_PM_H
> > +#include "i915_drv.h"
> >   #include "i915_request.h"
> >   #include "intel_engine_types.h"
> >   #include "intel_wakeref.h"
> > +#include "intel_gt_pm.h"
> >   static inline bool
> >   intel_engine_pm_is_awake(const struct intel_engine_cs *engine)
> > @@ -31,6 +33,21 @@ static inline bool intel_engine_pm_get_if_awake(struct intel_engine_cs *engine)
> >   	return intel_wakeref_get_if_active(&engine->wakeref);
> >   }
> > +static inline void intel_engine_pm_might_get(struct intel_engine_cs *engine)
> > +{
> > +	if (!intel_engine_is_virtual(engine)) {
> > +		intel_wakeref_might_get(&engine->wakeref);
> > +	} else {
> > +		struct intel_gt *gt = engine->gt;
> > +		struct intel_engine_cs *tengine;
> > +		intel_engine_mask_t tmp, mask = engine->mask;
> > +
> > +		for_each_engine_masked(tengine, gt, mask, tmp)
> > +			intel_wakeref_might_get(&tengine->wakeref);
> > +	}
> > +	intel_gt_pm_might_get(engine->gt);
> > +}
> > +
> >   static inline void intel_engine_pm_put(struct intel_engine_cs *engine)
> >   {
> >   	intel_wakeref_put(&engine->wakeref);
> > @@ -52,6 +69,21 @@ static inline void intel_engine_pm_flush(struct intel_engine_cs *engine)
> >   	intel_wakeref_unlock_wait(&engine->wakeref);
> >   }
> > +static inline void intel_engine_pm_might_put(struct intel_engine_cs *engine)
> > +{
> > +	if (!intel_engine_is_virtual(engine)) {
> > +		intel_wakeref_might_put(&engine->wakeref);
> > +	} else {
> > +		struct intel_gt *gt = engine->gt;
> > +		struct intel_engine_cs *tengine;
> > +		intel_engine_mask_t tmp, mask = engine->mask;
> > +
> > +		for_each_engine_masked(tengine, gt, mask, tmp)
> > +			intel_wakeref_might_put(&tengine->wakeref);
> > +	}
> > +	intel_gt_pm_might_put(engine->gt);
> > +}
> > +
> >   static inline struct i915_request *
> >   intel_engine_create_kernel_request(struct intel_engine_cs *engine)
> >   {
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > index 05de6c1af25b..bc898df7a48c 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > @@ -31,6 +31,11 @@ static inline bool intel_gt_pm_get_if_awake(struct intel_gt *gt)
> >   	return intel_wakeref_get_if_active(&gt->wakeref);
> >   }
> > +static inline void intel_gt_pm_might_get(struct intel_gt *gt)
> > +{
> > +	intel_wakeref_might_get(&gt->wakeref);
> > +}
> > +
> >   static inline void intel_gt_pm_put(struct intel_gt *gt)
> >   {
> >   	intel_wakeref_put(&gt->wakeref);
> > @@ -41,6 +46,11 @@ static inline void intel_gt_pm_put_async(struct intel_gt *gt)
> >   	intel_wakeref_put_async(&gt->wakeref);
> >   }
> > +static inline void intel_gt_pm_might_put(struct intel_gt *gt)
> > +{
> > +	intel_wakeref_might_put(&gt->wakeref);
> > +}
> > +
> >   #define with_intel_gt_pm(gt, tmp) \
> >   	for (tmp = 1, intel_gt_pm_get(gt); tmp; \
> >   	     intel_gt_pm_put(gt), tmp = 0)
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > index 17da2fea1bff..8b82da50c2bc 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -1571,7 +1571,12 @@ static int guc_context_pre_pin(struct intel_context *ce,
> >   static int guc_context_pin(struct intel_context *ce, void *vaddr)
> >   {
> > -	return __guc_context_pin(ce, ce->engine, vaddr);
> > +	int ret = __guc_context_pin(ce, ce->engine, vaddr);
> > +
> > +	if (likely(!ret && !intel_context_is_barrier(ce)))
> > +		intel_engine_pm_get(ce->engine);
> > +
> > +	return ret;
> >   }
> >   static void guc_context_unpin(struct intel_context *ce)
> > @@ -1580,6 +1585,9 @@ static void guc_context_unpin(struct intel_context *ce)
> >   	unpin_guc_id(guc, ce);
> >   	lrc_unpin(ce);
> > +
> > +	if (likely(!intel_context_is_barrier(ce)))
> > +		intel_engine_pm_put_async(ce->engine);
> >   }
> >   static void guc_context_post_unpin(struct intel_context *ce)
> > @@ -2341,8 +2349,30 @@ static int guc_virtual_context_pre_pin(struct intel_context *ce,
> >   static int guc_virtual_context_pin(struct intel_context *ce, void *vaddr)
> >   {
> >   	struct intel_engine_cs *engine = guc_virtual_get_sibling(ce->engine, 0);
> > +	int ret = __guc_context_pin(ce, engine, vaddr);
> > +	intel_engine_mask_t tmp, mask = ce->engine->mask;
> > +
> > +	if (likely(!ret))
> > +		for_each_engine_masked(engine, ce->engine->gt, mask, tmp)
> > +			intel_engine_pm_get(engine);
> > -	return __guc_context_pin(ce, engine, vaddr);
> > +	return ret;
> > +}
> > +
> > +static void guc_virtual_context_unpin(struct intel_context *ce)
> > +{
> > +	intel_engine_mask_t tmp, mask = ce->engine->mask;
> > +	struct intel_engine_cs *engine;
> > +	struct intel_guc *guc = ce_to_guc(ce);
> > +
> > +	GEM_BUG_ON(context_enabled(ce));
> > +	GEM_BUG_ON(intel_context_is_barrier(ce));
> > +
> > +	unpin_guc_id(guc, ce);
> > +	lrc_unpin(ce);
> > +
> > +	for_each_engine_masked(engine, ce->engine->gt, mask, tmp)
> > +		intel_engine_pm_put_async(engine);
> >   }
> >   static void guc_virtual_context_enter(struct intel_context *ce)
> > @@ -2379,7 +2409,7 @@ static const struct intel_context_ops virtual_guc_context_ops = {
> >   	.pre_pin = guc_virtual_context_pre_pin,
> >   	.pin = guc_virtual_context_pin,
> > -	.unpin = guc_context_unpin,
> > +	.unpin = guc_virtual_context_unpin,
> >   	.post_unpin = guc_context_post_unpin,
> >   	.ban = guc_context_ban,
> > diff --git a/drivers/gpu/drm/i915/intel_wakeref.h b/drivers/gpu/drm/i915/intel_wakeref.h
> > index 545c8f277c46..4f4c2e15e736 100644
> > --- a/drivers/gpu/drm/i915/intel_wakeref.h
> > +++ b/drivers/gpu/drm/i915/intel_wakeref.h
> > @@ -123,6 +123,12 @@ enum {
> >   	__INTEL_WAKEREF_PUT_LAST_BIT__
> >   };
> > +static inline void
> > +intel_wakeref_might_get(struct intel_wakeref *wf)
> > +{
> > +	might_lock(&wf->mutex);
> > +}
> > +
> >   /**
> >    * intel_wakeref_put_flags: Release the wakeref
> >    * @wf: the wakeref
> > @@ -170,6 +176,12 @@ intel_wakeref_put_delay(struct intel_wakeref *wf, unsigned long delay)
> >   			    FIELD_PREP(INTEL_WAKEREF_PUT_DELAY, delay));
> >   }
> > +static inline void
> > +intel_wakeref_might_put(struct intel_wakeref *wf)
> > +{
> > +	might_lock(&wf->mutex);
> > +}
> > +
> >   /**
> >    * intel_wakeref_lock: Lock the wakeref (mutex)
> >    * @wf: the wakeref
>