Re: [PATCH v4 1/5] drm/gpusvm: Introduce devmem_only flag for allocation

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Apr 22, 2025 at 10:04:11AM -0700, Matthew Brost wrote:
> From: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> 
> This commit adds a new flag, devmem_only, to the drm_gpusvm structure. The
> purpose of this flag is to ensure that the get_pages function allocates
> memory exclusively from the device's memory. If the allocation from
> device memory fails, the function will return an -EFAULT error.
> 
> v3:
>  - s/vram_only/devmem_only/
> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> ---
>  drivers/gpu/drm/drm_gpusvm.c | 5 +++++
>  include/drm/drm_gpusvm.h     | 2 ++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
> index 38431e8360e7..edf107809d20 100644
> --- a/drivers/gpu/drm/drm_gpusvm.c
> +++ b/drivers/gpu/drm/drm_gpusvm.c
> @@ -1454,6 +1454,11 @@ int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
>  				goto err_unmap;
>  			}
>  
> +			if (ctx->devmem_only) {
> +				err = -EFAULT;
> +				goto err_unmap;
> +			}
> +
>  			addr = dma_map_page(gpusvm->drm->dev,
>  					    page, 0,
>  					    PAGE_SIZE << order,
> diff --git a/include/drm/drm_gpusvm.h b/include/drm/drm_gpusvm.h
> index df120b4d1f83..9fd25fc880a4 100644
> --- a/include/drm/drm_gpusvm.h
> +++ b/include/drm/drm_gpusvm.h
> @@ -286,6 +286,7 @@ struct drm_gpusvm {
>   * @in_notifier: entering from a MMU notifier
>   * @read_only: operating on read-only memory
>   * @devmem_possible: possible to use device memory
> + * @devmem_only: use only device memory
>   *
>   * Context that is DRM GPUSVM is operating in (i.e. user arguments).
>   */
> @@ -294,6 +295,7 @@ struct drm_gpusvm_ctx {
>  	unsigned int in_notifier :1;
>  	unsigned int read_only :1;
>  	unsigned int devmem_possible :1;
> +	unsigned int devmem_only :1;
>  };
>  
>  int drm_gpusvm_init(struct drm_gpusvm *gpusvm,
> -- 
> 2.34.1
>