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

[Christian König]

Am 03.09.24 um 17:22 schrieb Thomas Hellström:
> On Tue, 2024-09-03 at 17:14 +0200, Christian König wrote:
>> 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.
> Yes, we could probably do that, although that means changing
> ttm_device_init() in all drivers.
>
> And if doing that, then I think we should coalesce all bool arguments
> to a flags argument to make the callers more readable.
>
> What do you think?

Works for me.

Christian.

>
> /Thomas
>
>
>
>> 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;