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

["Ghimiray, Himal Prasad" <himal.prasad.ghimiray@intel.com>]

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


The issue is not only limited to LNL but is also observed on BMG and
DG2. As far as I know, other host CPUs are not eECORES, so the reason
for failure on BMG won’t be the same. In my opinion, we should limit
this workaround to LNL and continue debugging BMG to find the root
cause.

Probably it will be better to add platform check even on e51527233804.

On BMG and DG2:
https://patchwork.freedesktop.org/series/140267/ series from Matt might 
help solve this.

BR
Himal

> 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);
> +
>   	spin_lock_irq(&gt->tlb_invalidation.pending_lock);
>   	list_for_each_entry_safe(fence, next,
>   				 &gt->tlb_invalidation.pending_fences, link) {