Re: [PATCH] drm/xe/guc/tlb: Flush g2h worker in case of tlb timeout

[Nirmoy Das <nirmoy.das@linux.intel.com>]

On 10/24/2024 12:02 PM, Nilawar, Badal wrote:
>
>
> On 23-10-2024 20:43, Nirmoy Das wrote:
>> Flush the g2h worker explicitly if TLB timeout happens which is
>> observed on LNL and that points recent scheduling issue with E-cores.
>> This is similar to the recent fix:
>> commit e51527233804 ("drm/xe/guc/ct: Flush g2h worker in case of g2h
>> response timeout") and should be removed once there is E core
>> scheduling fix.
>>
>> Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/2687
>> Cc: Badal Nilawar <badal.nilawar@intel.com>
>> Cc: Matthew Brost <matthew.brost@intel.com>
>> Cc: Matthew Auld <matthew.auld@intel.com>
>> Cc: John Harrison <John.C.Harrison@Intel.com>
>> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
>> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
>> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
>> index 773de1f08db9..2c327dccbd74 100644
>> --- a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
>> +++ b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
>> @@ -72,6 +72,15 @@ static void xe_gt_tlb_fence_timeout(struct work_struct *work)
>>       struct xe_device *xe = gt_to_xe(gt);
>>       struct xe_gt_tlb_invalidation_fence *fence, *next;
>>   +    /*
>> +     * This is analogous to e51527233804 ("drm/xe/guc/ct: Flush g2h worker
>> +     * in case of g2h response timeout")
>> +     *
>> +     * TODO: Drop this change once workqueue scheduling delay issue is
>> +     * fixed on LNL Hybrid CPU.
>> +     */
>> +    flush_work(&gt->uc.guc.ct.g2h_worker);
>
> I didn't get the idea of flushing g2h worker here. Moreover AFAIK tlb invalidation is handled in fast path xe_guc_ct_fast_path i.e. in IRQ handler itself. Is this change solving the issue.

AFAIU g2h worker can also handle TLB_INVALIDATION_DONE message from GuC(process_g2h_msg). This indeed fixes the issue from me for LNL.


Regards,

Nirmoy

>
> static inline void xe_guc_ct_irq_handler(struct xe_guc_ct *ct)
> {
>         if (!xe_guc_ct_enabled(ct))
>                 return;
>
>         wake_up_all(&ct->wq);
>         queue_work(ct->g2h_wq, &ct->g2h_worker);
>         xe_guc_ct_fast_path(ct);
> }
>
> Regards,
> Badal
>
>> +
>>       spin_lock_irq(&gt->tlb_invalidation.pending_lock);
>>       list_for_each_entry_safe(fence, next,
>>                    &gt->tlb_invalidation.pending_fences, link) {
>