On Tue, Aug 10, 2021 at 08:43:50AM +0200, Daniel Vetter wrote: > On Mon, Aug 09, 2021 at 06:11:37PM +0000, Matthew Brost wrote: > > On Mon, Aug 09, 2021 at 04:23:42PM +0200, Daniel Vetter wrote: > > > On Tue, Aug 03, 2021 at 03:29:07PM -0700, 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. > > > > > > > > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx> > > > > --- > > > > drivers/gpu/drm/i915/Makefile | 1 + > > > > .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 36 +++++++++++++++++-- > > > > 2 files changed, 34 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile > > > > index 903de270f2db..5e3a1e2095b0 100644 > > > > --- a/drivers/gpu/drm/i915/Makefile > > > > +++ b/drivers/gpu/drm/i915/Makefile > > > > @@ -103,6 +103,7 @@ gt-y += \ > > > > gt/intel_gt_clock_utils.o \ > > > > gt/intel_gt_irq.o \ > > > > gt/intel_gt_pm.o \ > > > > + gt/intel_gt_pm_unpark_work.o \ > > > > > > This file isn't here? > > > > > > > Yep, included this in the wrong patch. Should be in: > > https://patchwork.freedesktop.org/patch/448462/?series=92789&rev=2 > > > > > Also pm stuff tends to have very nasty locking requirements, doing special > > > stuff like this in the backend tends to lead to really big surprises. I > > > think two options to make sure our locking design stays consistent: > > > - Lift this to generic code. > > > > Not sure I'm following this, intel_engine_pm_get/put are generic calls. > > Those calls should have all the correct annoations. If they don't we can > > add them. > > But you only call them in the GuC backend, not in all of them. Which is an > inconsistency in locking, and unfortunately runtime pm is extremely nasty, > so having potentially very divergent locking behind the same interface in > the same driver is a recipe for an unmaintainable mess. > > Iow, if the high-level code runs on execlist or the ringbuffer backend we > still need to go through at least the lockdep motions of what you're > adding here. > > This is similar in spirit to all the might_sleep/might_lock calls we have > all over the kernel where in many cases something doesn't happen, but we > need to make sure it's allowed to have a consistent design. > > So essentially in the intel_context_pin and all these functions put a > intel_engine_pm_might_get (which compiles out without debugging enabled), > unconditionally, across all platforms and sched backends. > Ok, I see your point here. We currently don't have a intel_engine_pm_might_get but I think this translates to roughly: might_lock(engine_pm_wf_mutex) intel_gt_pm_might_get Will dig in a big a more and add the annotations to the next rev. Matt > In general I think backend specific locking (irrespective of what kind of > backend or interface you implement) is a pretty bad idea in the kernel, > and needs to be avoided if at all possible. Avoid here means "pull the > might_lock/might_sleep/might_whatever checks into generic code". > -Daniel > > > Matt > > > > > - expose some engine_pm_migt_get/put() calls which do have the right set > > > of might_lock annoations, and call those in the generic code. > > > > > > Imo the worst kernel abstractions are those where all implementations > > > look&act the same, except for locking. Unfortunately i915-gem code is full > > > of this stuff, and we need to stop this by enlisting lockdep to check the > > > contracts for us. > > > -Daniel > > > > > > > gt/intel_gt_pm_irq.o \ > > > > gt/intel_gt_requests.o \ > > > > gt/intel_gtt.o \ > > > > 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 7fe4d1559a81..c5d9548bfd00 100644 > > > > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c > > > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c > > > > @@ -2056,7 +2056,12 @@ 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) > > > > @@ -2067,6 +2072,9 @@ static void guc_context_unpin(struct intel_context *ce) > > > > > > > > unpin_guc_id(guc, ce, true); > > > > lrc_unpin(ce); > > > > + > > > > + if (likely(!intel_context_is_barrier(ce))) > > > > + intel_engine_pm_put(ce->engine); > > > > } > > > > > > > > static void guc_context_post_unpin(struct intel_context *ce) > > > > @@ -3002,8 +3010,30 @@ 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, true); > > > > + lrc_unpin(ce); > > > > + > > > > + for_each_engine_masked(engine, ce->engine->gt, mask, tmp) > > > > + intel_engine_pm_put(engine); > > > > } > > > > > > > > static void guc_virtual_context_enter(struct intel_context *ce) > > > > @@ -3040,7 +3070,7 @@ 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, > > > > -- > > > > 2.28.0 > > > > > > > > > > -- > > > Daniel Vetter > > > Software Engineer, Intel Corporation > > > http://blog.ffwll.ch > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch
