Re: [Intel-gfx] [PATCH 06/27] drm/i915/guc: Take engine PM when a context is pinned with GuC submission

Matthew Brost
2021-09-14T01:17:15Z

On Mon, Sep 13, 2021 at 03:26:29PM -0700, John Harrison wrote:
> On 9/9/2021 17:41, Matthew Brost wrote:
> > On Thu, Sep 09, 2021 at 03:46:43PM -0700, John Harrison wrote:
> > > On 8/20/2021 15:44, 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.
> > > As with earlier PM patch, needs more explanation of what the problem is and
> > > why it is only now a problem.
> > >
> > >
> > Same explaination, will add here.
> >
> > > > v2:
> > > > (Daniel Vetter)
> > > > - Add might_lock annotations to pin / unpin function
> > > >
> > > > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > > > ---
> > > > drivers/gpu/drm/i915/gt/intel_context.c | 3 ++
> > > > drivers/gpu/drm/i915/gt/intel_engine_pm.h | 15 ++++++++
> > > > 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, 73 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> > > > index c8595da64ad8..508cfe5770c0 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;
> > > > @@ -313,6 +315,7 @@ void __intel_context_do_unpin(struct intel_context *ce, int sub)
> > > > return;
> > > > CE_TRACE(ce, "unpin\n");
> > > > + intel_engine_pm_might_put(ce->engine);
> > > > ce->ops->unpin(ce);
> > > > ce->ops->post_unpin(ce);
> > > > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.h b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> > > > index 17a5028ea177..3fe2ae1bcc26 100644
> > > > --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> > > > +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> > > > @@ -9,6 +9,7 @@
> > > > #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 +32,13 @@ 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);
> > > Why doesn't this need to iterate through the physical engines of the virtual
> > > engine?
> > >
> > Yea, technically it should. This is just an annotation though to check
> > if we do something horribly wrong in our code. If we use any physical
> > engine in our stack this annotation should pop and we can fix it. I just
> > don't see what making this 100% correct for virtual engines buys us. If
> > you want I can fix this but thinking the more complex we make this
> > annotation the less likely it just gets compiled out with lockdep off
> > which is what we are aiming for.
> But if the annotation is missing a fundamental lock then it is surely not
> actually going to do any good? Not sure if you need to iterate over all
> child engines + parent but it seems like you should be calling might_lock()
> on at least one engine's mutex to feed the lockdep annotation.
>

These are all inline functions so the compiler to be able to compile
this out if lockdep is disabled. I'll fix this in the next rev.

Matt

> John.
>
> > Matt
> >
> > > John.
> > >
> > > > + 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 +60,13 @@ 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);
> > > > + 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 a17bf0d4592b..3c173033ce23 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 dbf919801de2..e0eed70f9b92 100644
> > > > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > > > @@ -1550,7 +1550,12 @@ 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)
> > > > @@ -1559,6 +1564,9 @@ 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)
> > > > @@ -2328,8 +2336,30 @@ 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)
> > > > @@ -2366,7 +2396,7 @@ 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 ef7e6a698e8a..dd530ae028e0 100644
> > > > --- a/drivers/gpu/drm/i915/intel_wakeref.h
> > > > +++ b/drivers/gpu/drm/i915/intel_wakeref.h
> > > > @@ -124,6 +124,12 @@ 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
> > > > @@ -171,6 +177,12 @@ 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
>