Re: [PATCH 10/10] drm/xe: Kill xe_device_mem_access_{get*,put}

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Wed, 06 Mar 2024 16:15:54 -0800, Rodrigo Vivi wrote:
>

Hi Rodrigo/Matt,

> @@ -409,14 +410,14 @@ static int __xe_ggtt_insert_bo_at(struct xe_ggtt *ggtt, struct xe_bo *bo,
>	if (err)
>		return err;
>
> -	xe_device_mem_access_get(tile_to_xe(ggtt->tile));
> +	xe_pm_runtime_get_noresume(tile_to_xe(ggtt->tile));
>	mutex_lock(&ggtt->lock);
>	err = drm_mm_insert_node_in_range(&ggtt->mm, &bo->ggtt_node, bo->size,
>					  alignment, 0, start, end, 0);
>	if (!err)
>		xe_ggtt_map_bo(ggtt, bo);
>	mutex_unlock(&ggtt->lock);
> -	xe_device_mem_access_put(tile_to_xe(ggtt->tile));
> +	xe_pm_runtime_put(tile_to_xe(ggtt->tile));
>
>	return err;
>  }
> @@ -434,7 +435,7 @@ int xe_ggtt_insert_bo(struct xe_ggtt *ggtt, struct xe_bo *bo)
>
>  void xe_ggtt_remove_node(struct xe_ggtt *ggtt, struct drm_mm_node *node)
>  {
> -	xe_device_mem_access_get(tile_to_xe(ggtt->tile));
> +	xe_pm_runtime_get_noresume(tile_to_xe(ggtt->tile));
>	mutex_lock(&ggtt->lock);
>
>	xe_ggtt_clear(ggtt, node->start, node->size);
> @@ -444,7 +445,7 @@ void xe_ggtt_remove_node(struct xe_ggtt *ggtt, struct drm_mm_node *node)
>	xe_ggtt_invalidate(ggtt);
>
>	mutex_unlock(&ggtt->lock);
> -	xe_device_mem_access_put(tile_to_xe(ggtt->tile));
> +	xe_pm_runtime_put(tile_to_xe(ggtt->tile));

Do __xe_ggtt_insert_bo_at and xe_ggtt_insert_bo need a runtime_pm reference
held?

In this series: https://patchwork.freedesktop.org/series/121084/

I am not holding a runtime_pm reference when these functions are called and
it was fine with xe_device_mem_access_get/put (see
xe_oa_alloc_oa_buffer/xe_oa_free_oa_buffer if needed). But after changing
to xe_pm_runtime_get/put I now get this WARN:

[11614.356168] xe 0000:00:02.0: Missing outer runtime PM protection
[11614.356187] WARNING: CPU: 1 PID: 13075 at drivers/gpu/drm/xe/xe_pm.c:549 xe_pm_runtime_get_noresume+0x60/0x80 [xe]
...
[11614.356377] Call Trace:
[11614.356379]  <TASK>
[11614.356381]  ? __warn+0x7e/0x180
[11614.356387]  ? xe_pm_runtime_get_noresume+0x60/0x80 [xe]
[11614.356437]  ? report_bug+0x1c7/0x1d0
[11614.356442]  ? prb_read_valid+0x16/0x20
[11614.356447]  ? handle_bug+0x3c/0x70
[11614.356451]  ? exc_invalid_op+0x18/0x70
[11614.356453]  ? asm_exc_invalid_op+0x1a/0x20
[11614.356460]  ? xe_pm_runtime_get_noresume+0x60/0x80 [xe]
[11614.356507]  xe_ggtt_remove_node+0x22/0x80 [xe]
[11614.356546]  xe_ttm_bo_destroy+0xea/0xf0 [xe]
[11614.356579]  xe_oa_stream_destroy+0xf7/0x120 [xe]
[11614.356627]  xe_oa_release+0x35/0xc0 [xe]
[11614.356673]  __fput+0xa1/0x2d0
[11614.356679]  __x64_sys_close+0x37/0x80
[11614.356697]  do_syscall_64+0x6d/0x140
[11614.356700]  entry_SYSCALL_64_after_hwframe+0x71/0x79
[11614.356702] RIP: 0033:0x7f2b37314f67

Also, the WARN above happens only for 'free' but not for 'alloc' (so not
sure who gets the runtime_pm reference for 'alloc').

Holding the runtime_pm reference across alloc and free seems to be fine and
makes this WARN disappear. So maybe I should just do that? Just trying to
confirm.

Thanks.
--
Ashutosh