Re: [PATCH 2/2] drm/xe: Do not use CT lock in TLB code

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

On Wed, Apr 16, 2025 at 06:30:32PM +0000, Stuart Summers wrote:
> From: Nirmoy Das <nirmoy.das@intel.com>
> 
> Stop abusing CT lock for GT TLB invalidation fence seqno, add a
> dedicated lock.
> 
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>

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

> ---
>  drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c | 17 ++++++++++-------
>  drivers/gpu/drm/xe/xe_gt_types.h            | 13 ++++++++++---
>  2 files changed, 20 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> index 031c4d43f36b..c2bb53362d74 100644
> --- a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> +++ b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> @@ -3,6 +3,8 @@
>   * Copyright © 2023 Intel Corporation
>   */
>  
> +#include <drm/drm_managed.h>
> +
>  #include "xe_gt_tlb_invalidation.h"
>  
>  #include "abi/guc_actions_abi.h"
> @@ -123,7 +125,8 @@ int xe_gt_tlb_invalidation_init_early(struct xe_gt *gt)
>  	INIT_DELAYED_WORK(&gt->tlb_invalidation.fence_tdr,
>  			  xe_gt_tlb_fence_timeout);
>  
> -	return 0;
> +	return drmm_mutex_init(&gt_to_xe(gt)->drm,
> +			       &gt->tlb_invalidation.seqno_lock);
>  }
>  
>  /**
> @@ -142,7 +145,7 @@ void xe_gt_tlb_invalidation_reset(struct xe_gt *gt)
>  	 * appear.
>  	 */
>  
> -	mutex_lock(&gt->uc.guc.ct.lock);
> +	mutex_lock(&gt->tlb_invalidation.seqno_lock);
>  	spin_lock_irq(&gt->tlb_invalidation.pending_lock);
>  	cancel_delayed_work(&gt->tlb_invalidation.fence_tdr);
>  	/*
> @@ -162,7 +165,7 @@ void xe_gt_tlb_invalidation_reset(struct xe_gt *gt)
>  				 &gt->tlb_invalidation.pending_fences, link)
>  		invalidation_fence_signal(gt_to_xe(gt), fence);
>  	spin_unlock_irq(&gt->tlb_invalidation.pending_lock);
> -	mutex_unlock(&gt->uc.guc.ct.lock);
> +	mutex_unlock(&gt->tlb_invalidation.seqno_lock);
>  }
>  
>  static bool tlb_invalidation_seqno_past(struct xe_gt *gt, int seqno)
> @@ -195,13 +198,13 @@ static int send_tlb_invalidation(struct xe_guc *guc,
>  	 * need to be updated.
>  	 */
>  
> -	mutex_lock(&guc->ct.lock);
> +	mutex_lock(&gt->tlb_invalidation.seqno_lock);
>  	seqno = gt->tlb_invalidation.seqno;
>  	fence->seqno = seqno;
>  	trace_xe_gt_tlb_invalidation_fence_send(xe, fence);
>  	action[1] = seqno;
> -	ret = xe_guc_ct_send_locked(&guc->ct, action, len,
> -				    G2H_LEN_DW_TLB_INVALIDATE, 1);
> +	ret = xe_guc_ct_send(&guc->ct, action, len,
> +			     G2H_LEN_DW_TLB_INVALIDATE, 1);
>  	if (!ret) {
>  		spin_lock_irq(&gt->tlb_invalidation.pending_lock);
>  		/*
> @@ -232,7 +235,7 @@ static int send_tlb_invalidation(struct xe_guc *guc,
>  		if (!gt->tlb_invalidation.seqno)
>  			gt->tlb_invalidation.seqno = 1;
>  	}
> -	mutex_unlock(&guc->ct.lock);
> +	mutex_unlock(&gt->tlb_invalidation.seqno_lock);
>  	xe_gt_stats_incr(gt, XE_GT_STATS_ID_TLB_INVAL, 1);
>  
>  	return ret;
> diff --git a/drivers/gpu/drm/xe/xe_gt_types.h b/drivers/gpu/drm/xe/xe_gt_types.h
> index be81687cbe2b..4736a608a881 100644
> --- a/drivers/gpu/drm/xe/xe_gt_types.h
> +++ b/drivers/gpu/drm/xe/xe_gt_types.h
> @@ -187,17 +187,24 @@ struct xe_gt {
>  
>  	/** @tlb_invalidation: TLB invalidation state */
>  	struct {
> -		/** @tlb_invalidation.seqno: TLB invalidation seqno, protected by CT lock */
> +		/** @tlb_invalidation.seqno_lock: TLB invalidation seqno lock */
> +		struct mutex seqno_lock;
> +		/**
> +		 * @tlb_invalidation.seqno: TLB invalidation seqno, protected
> +		 * by @tlb_invalidation.seqno_lock
> +		 */
>  #define TLB_INVALIDATION_SEQNO_MAX	0x100000
>  		int seqno;
>  		/**
>  		 * @tlb_invalidation.seqno_recv: last received TLB invalidation seqno,
> -		 * protected by CT lock
> +		 * protected by @tlb_invalidation.seqno_lock (send) and
> +		 * @tlb_invalidation.pending_lock (send, recv)
>  		 */
>  		int seqno_recv;
>  		/**
>  		 * @tlb_invalidation.pending_fences: list of pending fences waiting TLB
> -		 * invaliations, protected by CT lock
> +		 * invaliations, protected by @tlb_invalidation.seqno_lock
> +		 * (send) and @tlb_invalidation.pending_lock (send, recv)
>  		 */
>  		struct list_head pending_fences;
>  		/**
> -- 
> 2.34.1
>