Re: [Intel-gfx] [PATCH] drm/i915/guc: Initialize GuC submission locks and queues early

["Ceraolo Spurio, Daniele" <daniele.ceraolospurio@intel.com>]

On 2/15/2022 1:09 AM, Tvrtko Ursulin wrote:
>
> On 15/02/2022 01:11, Daniele Ceraolo Spurio wrote:
>> Move initialization of submission-related spinlock, lists and workers to
>> init_early. This fixes an issue where if the GuC init fails we might
>> still try to get the lock in the context cleanup code. Note that it is
>
> What's the worst case impact on non-debug builds aka is Fixes: required?

There is no lock contention in this scenario and nothing is done within 
the locked section (because submission is not initialized and all 
contexts are marked as invalid), so no problems from the fact that the 
lock doesn't work. Is that enough to avoid a fixes tag?

Daniele

>
> Regards,
>
> Tvrtko
>
>> safe to call the GuC context cleanup code even if the init failed
>> because all contexts are initialized with an invalid GuC ID, which will
>> cause the GuC side of the cleanup to be skipped, so it is easier to just
>> make sure the variables are initialized than to special case the cleanup
>> to handle the case when they're not.
>>
>> References: https://gitlab.freedesktop.org/drm/intel/-/issues/4932
>> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
>> Cc: Matthew Brost <matthew.brost@intel.com>
>> Cc: John Harrison <John.C.Harrison@Intel.com>
>> ---
>>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 27 ++++++++++---------
>>   1 file changed, 14 insertions(+), 13 deletions(-)
>>
>> 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 b3a429a92c0da..2160da2c83cbf 100644
>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>> @@ -1818,24 +1818,11 @@ int intel_guc_submission_init(struct 
>> intel_guc *guc)
>>        */
>>       GEM_BUG_ON(!guc->lrc_desc_pool);
>>   -    xa_init_flags(&guc->context_lookup, XA_FLAGS_LOCK_IRQ);
>> -
>> -    spin_lock_init(&guc->submission_state.lock);
>> -    INIT_LIST_HEAD(&guc->submission_state.guc_id_list);
>> -    ida_init(&guc->submission_state.guc_ids);
>> - INIT_LIST_HEAD(&guc->submission_state.destroyed_contexts);
>> -    INIT_WORK(&guc->submission_state.destroyed_worker,
>> -          destroyed_worker_func);
>> -    INIT_WORK(&guc->submission_state.reset_fail_worker,
>> -          reset_fail_worker_func);
>> -
>>       guc->submission_state.guc_ids_bitmap =
>>           bitmap_zalloc(NUMBER_MULTI_LRC_GUC_ID(guc), GFP_KERNEL);
>>       if (!guc->submission_state.guc_ids_bitmap)
>>           return -ENOMEM;
>>   -    spin_lock_init(&guc->timestamp.lock);
>> -    INIT_DELAYED_WORK(&guc->timestamp.work, guc_timestamp_ping);
>>       guc->timestamp.ping_delay = (POLL_TIME_CLKS / 
>> gt->clock_frequency + 1) * HZ;
>>       guc->timestamp.shift = gpm_timestamp_shift(gt);
>>   @@ -3831,6 +3818,20 @@ static bool __guc_submission_selected(struct 
>> intel_guc *guc)
>>     void intel_guc_submission_init_early(struct intel_guc *guc)
>>   {
>> +    xa_init_flags(&guc->context_lookup, XA_FLAGS_LOCK_IRQ);
>> +
>> +    spin_lock_init(&guc->submission_state.lock);
>> +    INIT_LIST_HEAD(&guc->submission_state.guc_id_list);
>> +    ida_init(&guc->submission_state.guc_ids);
>> + INIT_LIST_HEAD(&guc->submission_state.destroyed_contexts);
>> +    INIT_WORK(&guc->submission_state.destroyed_worker,
>> +          destroyed_worker_func);
>> +    INIT_WORK(&guc->submission_state.reset_fail_worker,
>> +          reset_fail_worker_func);
>> +
>> +    spin_lock_init(&guc->timestamp.lock);
>> +    INIT_DELAYED_WORK(&guc->timestamp.work, guc_timestamp_ping);
>> +
>>       guc->submission_state.num_guc_ids = GUC_MAX_LRC_DESCRIPTORS;
>>       guc->submission_supported = __guc_submission_supported(guc);
>>       guc->submission_selected = __guc_submission_selected(guc);