[PATCH 2/4] drm/xe: store bind time pat index to xe_bo

[Matthew Auld]

On 18/01/2024 15:27, Juha-Pekka Heikkila wrote:
> Store pat index from xe_vma to xe_bo
> 
> Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila at gmail.com>
> ---
>   drivers/gpu/drm/xe/xe_pt.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> index de1030a47588..4b76db698878 100644
> --- a/drivers/gpu/drm/xe/xe_pt.c
> +++ b/drivers/gpu/drm/xe/xe_pt.c
> @@ -1252,6 +1252,10 @@ __xe_pt_bind_vma(struct xe_tile *tile, struct xe_vma *vma, struct xe_exec_queue
>   		return ERR_PTR(-ENOMEM);
>   	}
>   
> +	if (xe_vma_bo(vma)) {
> +		xe_vma_bo(vma)->pat_index = vma->pat_index;

Multiple mappings will trash this I think. Is that OK for your usecase? 
It can be useful to map the same resource as compressed and uncompressed 
to facilitate in-place decompression/compression.

Also would be good to be clear about what happens if the KMD doesn't do 
anything to prevent compression with non-tile4? Is it just a bit of 
display corruption or something much worse that we need to prevent? Is 
this just a best effort check to help userspace? Otherwise it is hard to 
evaluate how solid we need to be here in our checking to prevent this 
scenario. For example how is binding vs display races handled? What 
happens if the bind appears after the display check?

> +	}
> +
>   	fence = xe_migrate_update_pgtables(tile->migrate,
>   					   vm, xe_vma_bo(vma), q,
>   					   entries, num_entries,