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

John Harrison
2021-10-07T18:13:32Z

On 10/7/2021 08:05, Matthew Brost wrote:
> On Wed, Oct 06, 2021 at 08:06:41PM -0700, John Harrison wrote:
>> 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.
>>
>>
> Can add that back in.
>
>>> + /**
>>> + * @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?
>>
> It might, not really sure but agree the submission_state should be
> dropped. Think changed because of global find replace.
>
> Matt
Okay. With those nits fixed:
Reviewed by: John Harrison <John.C.Harrison@Intel.com>

>> 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);