Re: [Intel-xe] [PATCH v4 6/7] drm/xe/tlb: also update seqno_recv during reset

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Jul 05, 2023 at 05:06:09PM +0100, Matthew Auld wrote:
> We might have various kworkers waiting for TLB flushes to complete which
> are not tracked with an explicit TLB fence, however at this stage that
> will never happen since the CT is already disabled, so make sure we
> signal them here under the assumption that we have completed a full GT
> reset.
> 
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: José Roberto de Souza <jose.souza@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> index b38da572d268..51789ec9ad57 100644
> --- a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> +++ b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> @@ -89,10 +89,26 @@ invalidation_fence_signal(struct xe_gt_tlb_invalidation_fence *fence)
>   void xe_gt_tlb_invalidation_reset(struct xe_gt *gt)
>  {
>  	struct xe_gt_tlb_invalidation_fence *fence, *next;
> +	struct xe_guc *guc = &gt->uc.guc;
>  
> +	/*
> +	 * CT channel is already disabled at this point. No new TLB requests can
> +	 * appear.
> +	 */
> +
> +	mutex_lock(&gt->uc.guc.ct.lock);
>  	cancel_delayed_work(&gt->tlb_invalidation.fence_tdr);
> +	/*
> +	 * We might have various kworkers waiting for TLB flushes to complete
> +	 * which are not tracked with an explicit TLB fence, however at this
> +	 * stage that will never happen since the CT is already disabled, so
> +	 * make sure we signal them here under the assumption that we have
> +	 * completed a full GT reset.
> +	 */
> +	gt->tlb_invalidation.seqno_recv = gt->tlb_invalidation.seqno;
> +	smp_wmb();

The smp_wmb() probably isn't needed, this my mistake and have this wrong
in a places in the code. Barriers are not my strong point though so
maybe double check on this.

Otherwise LGTM.

With that:
Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> +	wake_up_all(&guc->ct.wq);
>  
> -	mutex_lock(&gt->uc.guc.ct.lock);
>  	list_for_each_entry_safe(fence, next,
>  				 &gt->tlb_invalidation.pending_fences, link)
>  		invalidation_fence_signal(fence);
> -- 
> 2.41.0
>