Re: [PATCH 04/11] drm/xe: Implement xe_pagefault_handler

[Francois Dugast <francois.dugast@intel.com>]

On Tue, Aug 05, 2025 at 11:22:35PM -0700, Matthew Brost wrote:
> Enqueue (copy) the input struct xe_pagefault into a queue (i.e., into a
> memory buffer) and schedule a worker to service it.
> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Francois Dugast <francois.dugast@intel.com>

> ---
>  drivers/gpu/drm/xe/xe_pagefault.c | 32 +++++++++++++++++++++++++++++--
>  1 file changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pagefault.c b/drivers/gpu/drm/xe/xe_pagefault.c
> index aef389e51612..98be3203a9df 100644
> --- a/drivers/gpu/drm/xe/xe_pagefault.c
> +++ b/drivers/gpu/drm/xe/xe_pagefault.c
> @@ -3,6 +3,8 @@
>   * Copyright © 2025 Intel Corporation
>   */
>  
> +#include <linux/circ_buf.h>
> +
>  #include <drm/drm_managed.h>
>  
>  #include "xe_device.h"
> @@ -156,6 +158,14 @@ void xe_pagefault_reset(struct xe_device *xe, struct xe_gt *gt)
>  		xe_pagefault_queue_reset(xe, gt, xe->usm.pf_queue + i);
>  }
>  
> +static bool xe_pagefault_queue_full(struct xe_pagefault_queue *pf_queue)
> +{
> +	lockdep_assert_held(&pf_queue->lock);
> +
> +	return CIRC_SPACE(pf_queue->head, pf_queue->tail, pf_queue->size) <=
> +		xe_pagefault_entry_size();
> +}
> +
>  /**
>   * xe_pagefault_handler() - Page fault handler
>   * @xe: xe device instance
> @@ -168,6 +178,24 @@ void xe_pagefault_reset(struct xe_device *xe, struct xe_gt *gt)
>   */
>  int xe_pagefault_handler(struct xe_device *xe, struct xe_pagefault *pf)
>  {
> -	/* TODO - implement */
> -	return 0;
> +	struct xe_pagefault_queue *pf_queue = xe->usm.pf_queue +
> +		(pf->consumer.asid % XE_PAGEFAULT_QUEUE_COUNT);
> +	unsigned long flags;
> +	bool full;
> +
> +	spin_lock_irqsave(&pf_queue->lock, flags);
> +	full = xe_pagefault_queue_full(pf_queue);
> +	if (!full) {
> +		memcpy(pf_queue->data + pf_queue->head, pf, sizeof(*pf));
> +		pf_queue->head = (pf_queue->head + xe_pagefault_entry_size()) %
> +			pf_queue->size;
> +		queue_work(xe->usm.pf_wq, &pf_queue->worker);
> +	} else {
> +		drm_warn(&xe->drm,
> +			 "PageFault Queue (%d) full, shouldn't be possible\n",
> +			 pf->consumer.asid % XE_PAGEFAULT_QUEUE_COUNT);
> +	}
> +	spin_unlock_irqrestore(&pf_queue->lock, flags);
> +
> +	return full ? -ENOSPC : 0;
>  }
> -- 
> 2.34.1
>