Re: [PATCH V14 3/9] drm/xe: Link LRC BO and its execution Queue

On 30-07-2026 15:41, Tejas Upadhyay wrote:
> To establish a link between an LRC BO (Logical Ring Context
> Buffer Object) and its corresponding execution Queue in the
> drm/xe driver, you need to store a back-pointer to the queue
> within the BO's private data structure. This allows the
> driver to identify and take corrective action on the specific
> queue if the LRC BO encounters an error (e.g., memory
> corruption or eviction issues).
> 
> V3(Sashiko):
> - Placeholder of 8 byte for non-lrc bo is acceptable
> - Assign bo-q is safe just use READ_ONCE/WRITE_ONCE
> V2(MattB):
> - Handle multiqueue
> 
> Signed-off-by: Tejas Upadhyay <[email protected]>
> ---
>   drivers/gpu/drm/xe/xe_bo_types.h   | 3 +++
>   drivers/gpu/drm/xe/xe_exec_queue.c | 6 ++++++
>   drivers/gpu/drm/xe/xe_lrc.c        | 1 +
>   3 files changed, 10 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo_types.h b/drivers/gpu/drm/xe/xe_bo_types.h
> index e45f24301050..a9c48e440669 100644
> --- a/drivers/gpu/drm/xe/xe_bo_types.h
> +++ b/drivers/gpu/drm/xe/xe_bo_types.h
> @@ -20,6 +20,7 @@
>   struct xe_device;
>   struct xe_mem_pool_node;
>   struct xe_vm;
> +struct xe_exec_queue;
>   
>   #define XE_BO_MAX_PLACEMENTS	3
>   
> @@ -42,6 +43,8 @@ struct xe_bo {
>   	u32 flags;
>   	/** @vm: VM this BO is attached to, for extobj this will be NULL */
>   	struct xe_vm *vm;
> +	/** @q: Queue this BO is attached to, mostly for LRC BO, NULL otherwise */
> +	struct xe_exec_queue *q;
>   	/** @tile: Tile this BO is attached to (kernel BO only) */
>   	struct xe_tile *tile;
>   	/** @placements: valid placements for this BO */
> diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
> index 38972b6e6d37..ab81a512fb41 100644
> --- a/drivers/gpu/drm/xe/xe_exec_queue.c
> +++ b/drivers/gpu/drm/xe/xe_exec_queue.c
> @@ -390,6 +390,12 @@ static int __xe_exec_queue_init(struct xe_exec_queue *q, u32 exec_queue_flags)
>   				goto err_lrc;
>   			}
>   
> +			/*
> +			 * The queue ref counts the LRCs, thus it safe for the LRC BO to hold a
> +			 * pointer to queue without reference.  The reader holds dma_resv (
> +			 * xe_bo_lock) which serializes with xe_lrc_finish().
> +			 */
> +			WRITE_ONCE(lrc->bo->q, xe_exec_queue_multi_queue_primary(q));
>   			xe_exec_queue_set_lrc(q, lrc, i);

Reviewed-by: Himal Prasad Ghimiray <[email protected]>

>   
>   			if (__lrc)
> diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
> index 3e7c995085d0..ee77106b06bc 100644
> --- a/drivers/gpu/drm/xe/xe_lrc.c
> +++ b/drivers/gpu/drm/xe/xe_lrc.c
> @@ -1066,6 +1066,7 @@ static void xe_lrc_set_ppgtt(struct xe_lrc *lrc, struct xe_vm *vm)
>   static void xe_lrc_finish(struct xe_lrc *lrc)
>   {
>   	xe_hw_fence_ctx_finish(&lrc->fence_ctx);
> +	WRITE_ONCE(lrc->bo->q, NULL);
>   	xe_bo_unpin_map_no_vm(lrc->bo);
>   	xe_bo_unpin_map_no_vm(lrc->seqno_bo);
>   }