Re: [PATCH v7 2/5] drm/pagemap: Drop source_peer_migrates flag and assume true

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Fri, 2026-04-10 at 13:59 -0700, Matthew Brost wrote:
> All current users of DRM pagemap set source_peer_migrates to true
> during
> migration, and it is unclear whether any user would ever want to
> disable
> this for performance reasons or for features such as compression. It
> is
> also questionable whether this flag could be made to work with
> high-speed fabric mapping APIs.
> 
> Drop the flag and make DRM pagemap unconditionally assume that
> source_peer_migrates is true.
> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> Reviewed-by: Francois Dugast <francois.dugast@intel.com>

Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>


> ---
>  drivers/gpu/drm/drm_pagemap.c | 10 ++++------
>  drivers/gpu/drm/xe/xe_svm.c   |  1 -
>  include/drm/drm_pagemap.h     |  9 ++-------
>  3 files changed, 6 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_pagemap.c
> b/drivers/gpu/drm/drm_pagemap.c
> index 5002049e0198..63f32cf6e1a7 100644
> --- a/drivers/gpu/drm/drm_pagemap.c
> +++ b/drivers/gpu/drm/drm_pagemap.c
> @@ -651,12 +651,10 @@ int drm_pagemap_migrate_to_devmem(struct
> drm_pagemap_devmem *devmem_allocation,
>  				own_pages++;
>  				goto next;
>  			}
> -			if (mdetails->source_peer_migrates) {
> -				cur.dpagemap = src_zdd->dpagemap;
> -				cur.ops = src_zdd-
> >devmem_allocation->ops;
> -				cur.device = cur.dpagemap->drm->dev;
> -				pages[i] = src_page;
> -			}
> +			cur.dpagemap = src_zdd->dpagemap;
> +			cur.ops = src_zdd->devmem_allocation->ops;
> +			cur.device = cur.dpagemap->drm->dev;
> +			pages[i] = src_page;
>  		}
>  		if (!pages[i]) {
>  			cur.dpagemap = NULL;
> diff --git a/drivers/gpu/drm/xe/xe_svm.c
> b/drivers/gpu/drm/xe/xe_svm.c
> index ba67355f64cb..e1651e70c8f0 100644
> --- a/drivers/gpu/drm/xe/xe_svm.c
> +++ b/drivers/gpu/drm/xe/xe_svm.c
> @@ -1055,7 +1055,6 @@ static int xe_drm_pagemap_populate_mm(struct
> drm_pagemap *dpagemap,
>  	struct xe_pagemap *xpagemap = container_of(dpagemap,
> typeof(*xpagemap), dpagemap);
>  	struct drm_pagemap_migrate_details mdetails = {
>  		.timeslice_ms = timeslice_ms,
> -		.source_peer_migrates = 1,
>  	};
>  	struct xe_vram_region *vr = xe_pagemap_to_vr(xpagemap);
>  	struct dma_fence *pre_migrate_fence = NULL;
> diff --git a/include/drm/drm_pagemap.h b/include/drm/drm_pagemap.h
> index 75e6ca58922d..95eb4b66b057 100644
> --- a/include/drm/drm_pagemap.h
> +++ b/include/drm/drm_pagemap.h
> @@ -329,17 +329,12 @@ struct drm_pagemap_devmem {
>   * struct drm_pagemap_migrate_details - Details to govern migration.
>   * @timeslice_ms: The time requested for the migrated pagemap pages
> to
>   * be present in @mm before being allowed to be migrated back.
> - * @can_migrate_same_pagemap: Whether the copy function as indicated
> by
> - * the @source_peer_migrates flag, can migrate device pages within a
> - * single drm_pagemap.
> - * @source_peer_migrates: Whether on p2p migration, The source
> drm_pagemap
> - * should use the copy_to_ram() callback rather than the destination
> - * drm_pagemap should use the copy_to_devmem() callback.
> + * @can_migrate_same_pagemap: Whether the copy function can migrate
> + * device pages within a single drm_pagemap.
>   */
>  struct drm_pagemap_migrate_details {
>  	unsigned long timeslice_ms;
>  	u32 can_migrate_same_pagemap : 1;
> -	u32 source_peer_migrates : 1;
>  };
>  
>  #if IS_ENABLED(CONFIG_ZONE_DEVICE)