Re: Patch "drm/ttm: Add ttm_bo_access" has been added to the 6.12-stable tree

[Christian König <christian.koenig@xxxxxxx>]

Am 02.02.25 um 05:33 schrieb Sasha Levin:
> This is a note to let you know that I've just added the patch titled
>
>      drm/ttm: Add ttm_bo_access
>
> to the 6.12-stable tree which can be found at:
>      http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

This isn't a bug fix but a new feature and therefore shouldn't be 
backported.

Regards,
Christian.

> The filename of the patch is:
>       drm-ttm-add-ttm_bo_access.patch
> and it can be found in the queue-6.12 subdirectory.
>
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@xxxxxxxxxxxxxxx> know about it.
>
>
>
> commit 73b922f15552bb5b47cbcca4b4d2b131b89b786d
> Author: Matthew Brost <matthew.brost@xxxxxxxxx>
> Date:   Tue Nov 26 09:46:09 2024 -0800
>
>      drm/ttm: Add ttm_bo_access
>      
>      [ Upstream commit 7d08df5d0bd3d12d14dcec773fcddbe3eed3a8e8 ]
>      
>      Non-contiguous VRAM cannot easily be mapped in TTM nor can non-visible
>      VRAM easily be accessed. Add ttm_bo_access, which is similar to
>      ttm_bo_vm_access, to access such memory.
>      
>      v4:
>       - Fix checkpatch warnings (CI)
>      v5:
>       - Fix checkpatch warnings (CI)
>      v6:
>       - Fix kernel doc (Auld)
>      v7:
>       - Move ttm_bo_access to ttm_bo_vm.c (Christian)
>      
>      Cc: Christian König <christian.koenig@xxxxxxx>
>      Reported-by: Christoph Manszewski <christoph.manszewski@xxxxxxxxx>
>      Suggested-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
>      Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
>      Tested-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
>      Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>
>      Reviewed-by: Christian König <christian.koenig@xxxxxxx>
>      Link: https://patchwork.freedesktop.org/patch/msgid/20241126174615.2665852-3-matthew.brost@xxxxxxxxx
>      Stable-dep-of: 5f7bec831f1f ("drm/xe: Use ttm_bo_access in xe_vm_snapshot_capture_delayed")
>      Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index 4212b8c91dd42..17667ab31ad4c 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -405,13 +405,25 @@ static int ttm_bo_vm_access_kmap(struct ttm_buffer_object *bo,
>   	return len;
>   }
>   
> -int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
> -		     void *buf, int len, int write)
> +/**
> + * ttm_bo_access - Helper to access a buffer object
> + *
> + * @bo: ttm buffer object
> + * @offset: access offset into buffer object
> + * @buf: pointer to caller memory to read into or write from
> + * @len: length of access
> + * @write: write access
> + *
> + * Utility function to access a buffer object. Useful when buffer object cannot
> + * be easily mapped (non-contiguous, non-visible, etc...). Should not directly
> + * be exported to user space via a peak / poke interface.
> + *
> + * Returns:
> + * @len if successful, negative error code on failure.
> + */
> +int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
> +		  void *buf, int len, int write)
>   {
> -	struct ttm_buffer_object *bo = vma->vm_private_data;
> -	unsigned long offset = (addr) - vma->vm_start +
> -		((vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node))
> -		 << PAGE_SHIFT);
>   	int ret;
>   
>   	if (len < 1 || (offset + len) > bo->base.size)
> @@ -429,8 +441,8 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
>   		break;
>   	default:
>   		if (bo->bdev->funcs->access_memory)
> -			ret = bo->bdev->funcs->access_memory(
> -				bo, offset, buf, len, write);
> +			ret = bo->bdev->funcs->access_memory
> +				(bo, offset, buf, len, write);
>   		else
>   			ret = -EIO;
>   	}
> @@ -439,6 +451,18 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
>   
>   	return ret;
>   }
> +EXPORT_SYMBOL(ttm_bo_access);
> +
> +int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
> +		     void *buf, int len, int write)
> +{
> +	struct ttm_buffer_object *bo = vma->vm_private_data;
> +	unsigned long offset = (addr) - vma->vm_start +
> +		((vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node))
> +		 << PAGE_SHIFT);
> +
> +	return ttm_bo_access(bo, offset, buf, len, write);
> +}
>   EXPORT_SYMBOL(ttm_bo_vm_access);
>   
>   static const struct vm_operations_struct ttm_bo_vm_ops = {
> diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
> index 7b56d1ca36d75..e383dee82001e 100644
> --- a/include/drm/ttm/ttm_bo.h
> +++ b/include/drm/ttm/ttm_bo.h
> @@ -421,6 +421,8 @@ void ttm_bo_unpin(struct ttm_buffer_object *bo);
>   int ttm_bo_evict_first(struct ttm_device *bdev,
>   		       struct ttm_resource_manager *man,
>   		       struct ttm_operation_ctx *ctx);
> +int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
> +		  void *buf, int len, int write);
>   vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
>   			     struct vm_fault *vmf);
>   vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,