Re: [Intel-gfx] [PATCH 01/26] drm/i915/guc: Move GuC guc_id allocation under submission state sub-struct

John Harrison
2021-10-07T03:06:49Z

On 10/4/2021 15:06, Matthew Brost wrote:
> Move guc_id allocation under submission state sub-struct as a future
> patch will reuse the spin lock as a global submission state lock. Moving
> this into sub-struct makes ownership of fields / lock clear.
>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
> drivers/gpu/drm/i915/gt/intel_context_types.h | 6 +-
> drivers/gpu/drm/i915/gt/uc/intel_guc.h | 26 +++++----
> .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 56 ++++++++++---------
> 3 files changed, 47 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
> index 12252c411159..e7e3984aab78 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> @@ -197,18 +197,18 @@ struct intel_context {
> struct {
> /**
> * @id: handle which is used to uniquely identify this context
> - * with the GuC, protected by guc->contexts_lock
> + * with the GuC, protected by guc->submission_state.lock
> */
> u16 id;
> /**
> * @ref: the number of references to the guc_id, when
> * transitioning in and out of zero protected by
> - * guc->contexts_lock
> + * guc->submission_state.lock
> */
> atomic_t ref;
> /**
> * @link: in guc->guc_id_list when the guc_id has no refs but is
> - * still valid, protected by guc->contexts_lock
> + * still valid, protected by guc->submission_state.lock
> */
> struct list_head link;
> } guc_id;
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> index 5dd174babf7a..65b5e8eeef96 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> @@ -70,17 +70,21 @@ struct intel_guc {
> void (*disable)(struct intel_guc *guc);
> } interrupts;
>
> - /**
> - * @contexts_lock: protects guc_ids, guc_id_list, ce->guc_id.id, and
> - * ce->guc_id.ref when transitioning in and out of zero
> - */
> - spinlock_t contexts_lock;
> - /** @guc_ids: used to allocate unique ce->guc_id.id values */
> - struct ida guc_ids;
> - /**
> - * @guc_id_list: list of intel_context with valid guc_ids but no refs
> - */
> - struct list_head guc_id_list;
> + struct {
> + /**
> + * @lock: protects everything in submission_state
> + */
> + spinlock_t lock;
The old version also mentioned 'ce->guc_id.ref'. Should this not also
mention that transition? Or was the old comment inaccurate. I'm not
seeing any actual behaviour changes in the patch.

> + /**
> + * @guc_ids: used to allocate new guc_ids
> + */
> + struct ida guc_ids;
> + /**
> + * @guc_id_list: list of intel_context with valid guc_ids but no
> + * refs
> + */
> + struct list_head guc_id_list;
> + } submission_state;
>
> /**
> * @submission_supported: tracks whether we support GuC submission on
> 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 ba0de35f6323..ad5c18119d92 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -68,16 +68,16 @@
> * fence is used to stall all requests associated with this guc_id until the
> * corresponding G2H returns indicating the guc_id has been deregistered.
> *
> - * guc_ids:
> + * submission_state.guc_ids:
> * Unique number associated with private GuC context data passed in during
> * context registration / submission / deregistration. 64k available. Simple ida
> * is used for allocation.
> *
> - * Stealing guc_ids:
> - * If no guc_ids are available they can be stolen from another context at
> - * request creation time if that context is unpinned. If a guc_id can't be found
> - * we punt this problem to the user as we believe this is near impossible to hit
> - * during normal use cases.
> + * Stealing submission_state.guc_ids:
> + * If no submission_state.guc_ids are available they can be stolen from another
I would abbreviate this instance as well, submission_state.guc_id is
quite the mouthful. Unless this somehow magically links back to the
structure entry in the kerneldoc output?

John.

> + * context at request creation time if that context is unpinned. If a guc_id
> + * can't be found we punt this problem to the user as we believe this is near
> + * impossible to hit during normal use cases.
> *
> * Locking:
> * In the GuC submission code we have 3 basic spin locks which protect
> @@ -89,7 +89,7 @@
> * sched_engine can be submitting at a time. Currently only one sched_engine is
> * used for all of GuC submission but that could change in the future.
> *
> - * guc->contexts_lock
> + * guc->submission_state.lock
> * Protects guc_id allocation for the given GuC, i.e. only one context can be
> * doing guc_id allocation operations at a time for each GuC in the system.
> *
> @@ -103,7 +103,7 @@
> *
> * Lock ordering rules:
> * sched_engine->lock -> ce->guc_state.lock
> - * guc->contexts_lock -> ce->guc_state.lock
> + * guc->submission_state.lock -> ce->guc_state.lock
> *
> * Reset races:
> * When a full GT reset is triggered it is assumed that some G2H responses to
> @@ -1148,9 +1148,9 @@ int intel_guc_submission_init(struct intel_guc *guc)
>
> xa_init_flags(&guc->context_lookup, XA_FLAGS_LOCK_IRQ);
>
> - spin_lock_init(&guc->contexts_lock);
> - INIT_LIST_HEAD(&guc->guc_id_list);
> - ida_init(&guc->guc_ids);
> + spin_lock_init(&guc->submission_state.lock);
> + INIT_LIST_HEAD(&guc->submission_state.guc_id_list);
> + ida_init(&guc->submission_state.guc_ids);
>
> return 0;
> }
> @@ -1215,7 +1215,7 @@ static void guc_submit_request(struct i915_request *rq)
>
> static int new_guc_id(struct intel_guc *guc)
> {
> - return ida_simple_get(&guc->guc_ids, 0,
> + return ida_simple_get(&guc->submission_state.guc_ids, 0,
> GUC_MAX_LRC_DESCRIPTORS, GFP_KERNEL |
> __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
> }
> @@ -1223,7 +1223,8 @@ static int new_guc_id(struct intel_guc *guc)
> static void __release_guc_id(struct intel_guc *guc, struct intel_context *ce)
> {
> if (!context_guc_id_invalid(ce)) {
> - ida_simple_remove(&guc->guc_ids, ce->guc_id.id);
> + ida_simple_remove(&guc->submission_state.guc_ids,
> + ce->guc_id.id);
> reset_lrc_desc(guc, ce->guc_id.id);
> set_context_guc_id_invalid(ce);
> }
> @@ -1235,9 +1236,9 @@ static void release_guc_id(struct intel_guc *guc, struct intel_context *ce)
> {
> unsigned long flags;
>
> - spin_lock_irqsave(&guc->contexts_lock, flags);
> + spin_lock_irqsave(&guc->submission_state.lock, flags);
> __release_guc_id(guc, ce);
> - spin_unlock_irqrestore(&guc->contexts_lock, flags);
> + spin_unlock_irqrestore(&guc->submission_state.lock, flags);
> }
>
> static int steal_guc_id(struct intel_guc *guc)
> @@ -1245,10 +1246,10 @@ static int steal_guc_id(struct intel_guc *guc)
> struct intel_context *ce;
> int guc_id;
>
> - lockdep_assert_held(&guc->contexts_lock);
> + lockdep_assert_held(&guc->submission_state.lock);
>
> - if (!list_empty(&guc->guc_id_list)) {
> - ce = list_first_entry(&guc->guc_id_list,
> + if (!list_empty(&guc->submission_state.guc_id_list)) {
> + ce = list_first_entry(&guc->submission_state.guc_id_list,
> struct intel_context,
> guc_id.link);
>
> @@ -1273,7 +1274,7 @@ static int assign_guc_id(struct intel_guc *guc, u16 *out)
> {
> int ret;
>
> - lockdep_assert_held(&guc->contexts_lock);
> + lockdep_assert_held(&guc->submission_state.lock);
>
> ret = new_guc_id(guc);
> if (unlikely(ret < 0)) {
> @@ -1295,7 +1296,7 @@ static int pin_guc_id(struct intel_guc *guc, struct intel_context *ce)
> GEM_BUG_ON(atomic_read(&ce->guc_id.ref));
>
> try_again:
> - spin_lock_irqsave(&guc->contexts_lock, flags);
> + spin_lock_irqsave(&guc->submission_state.lock, flags);
>
> might_lock(&ce->guc_state.lock);
>
> @@ -1310,7 +1311,7 @@ static int pin_guc_id(struct intel_guc *guc, struct intel_context *ce)
> atomic_inc(&ce->guc_id.ref);
>
> out_unlock:
> - spin_unlock_irqrestore(&guc->contexts_lock, flags);
> + spin_unlock_irqrestore(&guc->submission_state.lock, flags);
>
> /*
> * -EAGAIN indicates no guc_id are available, let's retire any
> @@ -1346,11 +1347,12 @@ static void unpin_guc_id(struct intel_guc *guc, struct intel_context *ce)
> if (unlikely(context_guc_id_invalid(ce)))
> return;
>
> - spin_lock_irqsave(&guc->contexts_lock, flags);
> + spin_lock_irqsave(&guc->submission_state.lock, flags);
> if (!context_guc_id_invalid(ce) && list_empty(&ce->guc_id.link) &&
> !atomic_read(&ce->guc_id.ref))
> - list_add_tail(&ce->guc_id.link, &guc->guc_id_list);
> - spin_unlock_irqrestore(&guc->contexts_lock, flags);
> + list_add_tail(&ce->guc_id.link,
> + &guc->submission_state.guc_id_list);
> + spin_unlock_irqrestore(&guc->submission_state.lock, flags);
> }
>
> static int __guc_action_register_context(struct intel_guc *guc,
> @@ -1921,16 +1923,16 @@ static void guc_context_destroy(struct kref *kref)
> * returns indicating this context has been deregistered the guc_id is
> * returned to the pool of available guc_id.
> */
> - spin_lock_irqsave(&guc->contexts_lock, flags);
> + spin_lock_irqsave(&guc->submission_state.lock, flags);
> if (context_guc_id_invalid(ce)) {
> - spin_unlock_irqrestore(&guc->contexts_lock, flags);
> + spin_unlock_irqrestore(&guc->submission_state.lock, flags);
> __guc_context_destroy(ce);
> return;
> }
>
> if (!list_empty(&ce->guc_id.link))
> list_del_init(&ce->guc_id.link);
> - spin_unlock_irqrestore(&guc->contexts_lock, flags);
> + spin_unlock_irqrestore(&guc->submission_state.lock, flags);
>
> /* Seal race with Reset */
> spin_lock_irqsave(&ce->guc_state.lock, flags);