Re: [PATCH v5 4/5] drm/pagemap: Split drm_pagemap_migrate_map_pages into device / system

[Francois Dugast <francois.dugast@intel.com>]

On Thu, Feb 19, 2026 at 12:10:56PM -0800, Matthew Brost wrote:
> Split drm_pagemap_migrate_map_pages into device / system helpers clearly
> seperating these operations. Will help with upcoming changes to split
> IOVA allocation steps.

Side effect is that it makes the code a lot more readable. A couple of
nits below.

Reviewed-by: Francois Dugast <francois.dugast@intel.com>

> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> 
> ---
> v5:
>  - s/map_device_pages/map_device_private_pages (Thomas)
>  - Fix map_system_pages kernel doc (Thomas)
> ---
>  drivers/gpu/drm/drm_pagemap.c | 150 ++++++++++++++++++++++------------
>  1 file changed, 100 insertions(+), 50 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
> index 32535ab01c0f..ef8b9c69d1d4 100644
> --- a/drivers/gpu/drm/drm_pagemap.c
> +++ b/drivers/gpu/drm/drm_pagemap.c
> @@ -205,7 +205,8 @@ static void drm_pagemap_get_devmem_page(struct page *page,
>  }
>  
>  /**
> - * drm_pagemap_migrate_map_pages() - Map migration pages for GPU SVM migration
> + * drm_pagemap_migrate_map_device_private_pages() - Map device privaet migration

s/privaet/private/

> + * pages for GPU SVM migration
>   * @dev: The device performing the migration.
>   * @local_dpagemap: The drm_pagemap local to the migrating device.
>   * @pagemap_addr: Array to store DMA information corresponding to mapped pages.
> @@ -221,19 +222,22 @@ static void drm_pagemap_get_devmem_page(struct page *page,
>   *
>   * Returns: 0 on success, -EFAULT if an error occurs during mapping.
>   */
> -static int drm_pagemap_migrate_map_pages(struct device *dev,
> -					 struct drm_pagemap *local_dpagemap,
> -					 struct drm_pagemap_addr *pagemap_addr,
> -					 unsigned long *migrate_pfn,
> -					 unsigned long npages,
> -					 enum dma_data_direction dir,
> -					 const struct drm_pagemap_migrate_details *mdetails)
> +static int
> +drm_pagemap_migrate_map_device_private_pages(struct device *dev,
> +					     struct drm_pagemap *local_dpagemap,
> +					     struct drm_pagemap_addr *pagemap_addr,
> +					     unsigned long *migrate_pfn,
> +					     unsigned long npages,
> +					     enum dma_data_direction dir,
> +					     const struct drm_pagemap_migrate_details *mdetails)
>  {
>  	unsigned long num_peer_pages = 0, num_local_pages = 0, i;
>  
>  	for (i = 0; i < npages;) {
>  		struct page *page = migrate_pfn_to_page(migrate_pfn[i]);
> -		dma_addr_t dma_addr;
> +		struct drm_pagemap_zdd *zdd;
> +		struct drm_pagemap *dpagemap;
> +		struct drm_pagemap_addr addr;
>  		struct folio *folio;
>  		unsigned int order = 0;
>  
> @@ -243,36 +247,26 @@ static int drm_pagemap_migrate_map_pages(struct device *dev,
>  		folio = page_folio(page);
>  		order = folio_order(folio);
>  
> -		if (is_device_private_page(page)) {
> -			struct drm_pagemap_zdd *zdd = drm_pagemap_page_zone_device_data(page);
> -			struct drm_pagemap *dpagemap = zdd->dpagemap;
> -			struct drm_pagemap_addr addr;
> -
> -			if (dpagemap == local_dpagemap) {
> -				if (!mdetails->can_migrate_same_pagemap)
> -					goto next;
> +		WARN_ON_ONCE(!is_device_private_page(page));

Another nit: could we move this line ^ above that one:

    folio = page_folio(page);

so that the check is the first thing we do with that page, and also to
have a bit more symmetry with +drm_pagemap_migrate_map_system_pages().

Francois

>  
> -				num_local_pages += NR_PAGES(order);
> -			} else {
> -				num_peer_pages += NR_PAGES(order);
> -			}
> +		zdd = drm_pagemap_page_zone_device_data(page);
> +		dpagemap = zdd->dpagemap;
>  
> -			addr = dpagemap->ops->device_map(dpagemap, dev, page, order, dir);
> -			if (dma_mapping_error(dev, addr.addr))
> -				return -EFAULT;
> +		if (dpagemap == local_dpagemap) {
> +			if (!mdetails->can_migrate_same_pagemap)
> +				goto next;
>  
> -			pagemap_addr[i] = addr;
> +			num_local_pages += NR_PAGES(order);
>  		} else {
> -			dma_addr = dma_map_page(dev, page, 0, page_size(page), dir);
> -			if (dma_mapping_error(dev, dma_addr))
> -				return -EFAULT;
> -
> -			pagemap_addr[i] =
> -				drm_pagemap_addr_encode(dma_addr,
> -							DRM_INTERCONNECT_SYSTEM,
> -							order, dir);
> +			num_peer_pages += NR_PAGES(order);
>  		}
>  
> +		addr = dpagemap->ops->device_map(dpagemap, dev, page, order, dir);
> +		if (dma_mapping_error(dev, addr.addr))
> +			return -EFAULT;
> +
> +		pagemap_addr[i] = addr;
> +
>  next:
>  		i += NR_PAGES(order);
>  	}
> @@ -287,6 +281,60 @@ static int drm_pagemap_migrate_map_pages(struct device *dev,
>  	return 0;
>  }
>  
> +/**
> + * drm_pagemap_migrate_map_system_pages() - Map system or device coherent
> + * migration pages for GPU SVM migration
> + * @dev: The device performing the migration.
> + * @pagemap_addr: Array to store DMA information corresponding to mapped pages.
> + * @migrate_pfn: Array of page frame numbers of system pages or peer pages to map.
> + * @npages: Number of system or device coherent pages to map.
> + * @dir: Direction of data transfer (e.g., DMA_BIDIRECTIONAL)
> + *
> + * This function maps pages of memory for migration usage in GPU SVM. It
> + * iterates over each page frame number provided in @migrate_pfn, maps the
> + * corresponding page, and stores the DMA address in the provided @dma_addr
> + * array.
> + *
> + * Returns: 0 on success, -EFAULT if an error occurs during mapping.
> + */
> +static int
> +drm_pagemap_migrate_map_system_pages(struct device *dev,
> +				     struct drm_pagemap_addr *pagemap_addr,
> +				     unsigned long *migrate_pfn,
> +				     unsigned long npages,
> +				     enum dma_data_direction dir)
> +{
> +	unsigned long i;
> +
> +	for (i = 0; i < npages;) {
> +		struct page *page = migrate_pfn_to_page(migrate_pfn[i]);
> +		dma_addr_t dma_addr;
> +		struct folio *folio;
> +		unsigned int order = 0;
> +
> +		if (!page)
> +			goto next;
> +
> +		WARN_ON_ONCE(is_device_private_page(page));
> +		folio = page_folio(page);
> +		order = folio_order(folio);
> +
> +		dma_addr = dma_map_page(dev, page, 0, page_size(page), dir);
> +		if (dma_mapping_error(dev, dma_addr))
> +			return -EFAULT;
> +
> +		pagemap_addr[i] =
> +			drm_pagemap_addr_encode(dma_addr,
> +						DRM_INTERCONNECT_SYSTEM,
> +						order, dir);
> +
> +next:
> +		i += NR_PAGES(order);
> +	}
> +
> +	return 0;
> +}
> +
>  /**
>   * drm_pagemap_migrate_unmap_pages() - Unmap pages previously mapped for GPU SVM migration
>   * @dev: The device for which the pages were mapped
> @@ -347,9 +395,13 @@ drm_pagemap_migrate_remote_to_local(struct drm_pagemap_devmem *devmem,
>  				    const struct drm_pagemap_migrate_details *mdetails)
>  
>  {
> -	int err = drm_pagemap_migrate_map_pages(remote_device, remote_dpagemap,
> -						pagemap_addr, local_pfns,
> -						npages, DMA_FROM_DEVICE, mdetails);
> +	int err = drm_pagemap_migrate_map_device_private_pages(remote_device,
> +							       remote_dpagemap,
> +							       pagemap_addr,
> +							       local_pfns,
> +							       npages,
> +							       DMA_FROM_DEVICE,
> +							       mdetails);
>  
>  	if (err)
>  		goto out;
> @@ -368,12 +420,11 @@ drm_pagemap_migrate_sys_to_dev(struct drm_pagemap_devmem *devmem,
>  			       struct page *local_pages[],
>  			       struct drm_pagemap_addr pagemap_addr[],
>  			       unsigned long npages,
> -			       const struct drm_pagemap_devmem_ops *ops,
> -			       const struct drm_pagemap_migrate_details *mdetails)
> +			       const struct drm_pagemap_devmem_ops *ops)
>  {
> -	int err = drm_pagemap_migrate_map_pages(devmem->dev, devmem->dpagemap,
> -						pagemap_addr, sys_pfns, npages,
> -						DMA_TO_DEVICE, mdetails);
> +	int err = drm_pagemap_migrate_map_system_pages(devmem->dev,
> +						       pagemap_addr, sys_pfns,
> +						       npages, DMA_TO_DEVICE);
>  
>  	if (err)
>  		goto out;
> @@ -437,7 +488,7 @@ static int drm_pagemap_migrate_range(struct drm_pagemap_devmem *devmem,
>  						     &pages[last->start],
>  						     &pagemap_addr[last->start],
>  						     cur->start - last->start,
> -						     last->ops, mdetails);
> +						     last->ops);
>  
>  out:
>  	*last = *cur;
> @@ -942,7 +993,6 @@ EXPORT_SYMBOL(drm_pagemap_put);
>  int drm_pagemap_evict_to_ram(struct drm_pagemap_devmem *devmem_allocation)
>  {
>  	const struct drm_pagemap_devmem_ops *ops = devmem_allocation->ops;
> -	struct drm_pagemap_migrate_details mdetails = {};
>  	unsigned long npages, mpages = 0;
>  	struct page **pages;
>  	unsigned long *src, *dst;
> @@ -981,10 +1031,10 @@ int drm_pagemap_evict_to_ram(struct drm_pagemap_devmem *devmem_allocation)
>  	if (err || !mpages)
>  		goto err_finalize;
>  
> -	err = drm_pagemap_migrate_map_pages(devmem_allocation->dev,
> -					    devmem_allocation->dpagemap, pagemap_addr,
> -					    dst, npages, DMA_FROM_DEVICE,
> -					    &mdetails);
> +	err = drm_pagemap_migrate_map_system_pages(devmem_allocation->dev,
> +						   pagemap_addr,
> +						   dst, npages,
> +						   DMA_FROM_DEVICE);
>  	if (err)
>  		goto err_finalize;
>  
> @@ -1045,7 +1095,6 @@ static int __drm_pagemap_migrate_to_ram(struct vm_area_struct *vas,
>  		MIGRATE_VMA_SELECT_DEVICE_COHERENT,
>  		.fault_page	= page,
>  	};
> -	struct drm_pagemap_migrate_details mdetails = {};
>  	struct drm_pagemap_zdd *zdd;
>  	const struct drm_pagemap_devmem_ops *ops;
>  	struct device *dev = NULL;
> @@ -1103,8 +1152,9 @@ static int __drm_pagemap_migrate_to_ram(struct vm_area_struct *vas,
>  	if (err)
>  		goto err_finalize;
>  
> -	err = drm_pagemap_migrate_map_pages(dev, zdd->dpagemap, pagemap_addr, migrate.dst, npages,
> -					    DMA_FROM_DEVICE, &mdetails);
> +	err = drm_pagemap_migrate_map_system_pages(dev, pagemap_addr,
> +						   migrate.dst, npages,
> +						   DMA_FROM_DEVICE);
>  	if (err)
>  		goto err_finalize;
>  
> -- 
> 2.34.1
>