[PATCH v6 9/9] drm/xe/vf: Rebase exec queue parallel commands during migration recovery

[Michał Winiarski]

On Fri, Jul 04, 2025 at 11:02:28PM +0200, Tomasz Lis wrote:
> Parallel exec queues have an additional command streamer buffer which holds
> a GGTT reference to data within context status. The GGTT references have to
> be fixed after VF migration.
> 
> Signed-off-by: Tomasz Lis <tomasz.lis at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_submit.c | 26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
> index 37584a064574..96b94f7fcc31 100644
> --- a/drivers/gpu/drm/xe/xe_guc_submit.c
> +++ b/drivers/gpu/drm/xe/xe_guc_submit.c
> @@ -693,6 +693,27 @@ static void wq_item_append(struct xe_exec_queue *q)
>  	parallel_write(xe, map, wq_desc.tail, q->guc->wqi_tail);
>  }
>  
> +static void wq_items_rebase(struct xe_exec_queue *q)
> +{
> +	struct xe_guc *guc = exec_queue_to_guc(q);
> +	struct xe_device *xe = guc_to_xe(guc);
> +	struct iosys_map map = xe_lrc_parallel_map(q->lrc[0]);
> +	int i = q->guc->wqi_head;
> +
> +	/* the ring starts after a header struct */
> +	iosys_map_incr(&map, offsetof(struct guc_submit_parallel_scratch, wq[0]));
> +
> +	while (i != q->guc->wqi_tail) {
> +		u32 len_dw, val;
> +
> +		val = xe_map_rd_ring_u32(xe, &map, i / sizeof(u32) + 0, WQ_SIZE / sizeof(u32));
> +		len_dw = FIELD_GET(WQ_LEN_MASK, val);
> +		val = xe_lrc_descriptor(q->lrc[0]);
> +		xe_map_wr_ring_u32(xe, &map, i / sizeof(u32) + 1, WQ_SIZE / sizeof(u32), val);
> +		i += len_dw * sizeof(u32);
> +	}

This type of constructs make me anxious, as it's relatively easy to turn
it into infinite loop. Can we rewrite it as a for loop? Or at least
something with a fixed number of iterations as a condition? (instead of
!= tail)
Or at the very least - add some asserts...

Thanks,
-Michał

> +}
> +
>  #define RESUME_PENDING	~0x0ull
>  static void submit_exec_queue(struct xe_exec_queue *q)
>  {
> @@ -2511,7 +2532,10 @@ void xe_guc_contexts_hwsp_rebase(struct xe_guc *guc, void *scratch)
>  	unsigned long index;
>  
>  	mutex_lock(&guc->submission_state.lock);
> -	xa_for_each(&guc->submission_state.exec_queue_lookup, index, q)
> +	xa_for_each(&guc->submission_state.exec_queue_lookup, index, q) {
>  		xe_exec_queue_contexts_hwsp_rebase(q, scratch);
> +		if (xe_exec_queue_is_parallel(q))
> +			wq_items_rebase(q);
> +	}
>  	mutex_unlock(&guc->submission_state.lock);
>  }
> -- 
> 2.25.1
>