[RFC PATCH] drm/ttm: Forward -ENOSPC to drivers requesting it

[Christian König]

Am 03.09.24 um 15:38 schrieb Thomas Hellström:
> Some user-space APIs distinguison between graphics memory OOMs and
> system (host) memory OOMs. To aid UMDs in determining the type of
> OOM, allow forwarding the ENOSPC from resource managers to drivers
> on calls to ttm_bo_validate().
>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Matthew Brost <matthew.brost at intel.com>
> Cc: dri-devel at lists.freedesktop.org
> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>

Ah yes that was on my TODO list as well.

> ---
>   drivers/gpu/drm/ttm/ttm_bo.c | 2 +-
>   include/drm/ttm/ttm_bo.h     | 3 +++
>   2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index dd867b5e744c..d9a320dc8130 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -836,7 +836,7 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
>   	} while (ret && force_space);
>   
>   	/* For backward compatibility with userspace */
> -	if (ret == -ENOSPC)
> +	if (ret == -ENOSPC && !ctx->forward_enospc)

Mhm, couldn't we put that into the bdev? I would rather like to keep the 
UAPI consistent at least per driver.

Christian.

>   		return -ENOMEM;
>   
>   	/*
> diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
> index 5804408815be..d3e12318d336 100644
> --- a/include/drm/ttm/ttm_bo.h
> +++ b/include/drm/ttm/ttm_bo.h
> @@ -174,6 +174,8 @@ struct ttm_bo_kmap_obj {
>    * BOs share the same reservation object.
>    * @force_alloc: Don't check the memory account during suspend or CPU page
>    * faults. Should only be used by TTM internally.
> + * @forward_enospc: Don't translate -ENOSPC errors from resource managers to
> + * -ENOMEM, but forward them to the driver.
>    * @resv: Reservation object to allow reserved evictions with.
>    * @bytes_moved: Statistics on how many bytes have been moved.
>    *
> @@ -185,6 +187,7 @@ struct ttm_operation_ctx {
>   	bool no_wait_gpu;
>   	bool gfp_retry_mayfail;
>   	bool allow_res_evict;
> +	bool forward_enospc;
>   	bool force_alloc;
>   	struct dma_resv *resv;
>   	uint64_t bytes_moved;