Re: [PATCH v3 4/6] drm/pagemap: dma-unmap pages before handling migration errors

["Ghimiray, Himal Prasad" <himal.prasad.ghimiray@intel.com>]

On 06-08-2026 04:40, Matthew Brost wrote:
> drm_pagemap_migrate_unmap_pages() relies on the pages array to determine
> which pages require DMA unmapping. However,
> drm_pagemap_migration_unlock_put_pages() clears the array as part of its
> cleanup, leaving drm_pagemap_migrate_unmap_pages() with no valid page
> information if it is called afterward.
> 
> Call drm_pagemap_migrate_unmap_pages() before
> drm_pagemap_migration_unlock_put_pages() so the pages array remains
> valid during DMA unmapping.
> 
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Fixes: f86ad0ed620c ("drm/gpusvm, drm/pagemap: Move migration functionality to drm_pagemap")
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Lorenzo Stoakes <ljs@kernel.org>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
> Cc: Liam R. Howlett <liam@infradead.org>
> Cc: Nico Pache <nico.pache@linux.dev>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Dev Jain <dev.jain@arm.com>
> Cc: Barry Song <baohua@kernel.org>
> Cc: Lance Yang <lance.yang@linux.dev>
> Cc: Usama Arif <usama.arif@linux.dev>
> Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
> Cc: Rakie Kim <rakie.kim@sk.com>
> Cc: Byungchul Park <byungchul@sk.com>
> Cc: Gregory Price <gourry@gourry.net>
> Cc: Ying Huang <ying.huang@linux.alibaba.com>
> Cc: Alistair Popple <apopple@nvidia.com>
> Cc: Balbir Singh <balbirs@nvidia.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Simona Vetter <simona@ffwll.ch>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Cc: Francois Dugast <francois.dugast@intel.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Cc: stable@vger.kernel.org
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/drm_pagemap.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
> index 892b325fa99b..aef1fcea663d 100644
> --- a/drivers/gpu/drm/drm_pagemap.c
> +++ b/drivers/gpu/drm/drm_pagemap.c
> @@ -1175,12 +1175,12 @@ int drm_pagemap_evict_to_ram(struct drm_pagemap_devmem *devmem_allocation)
>   		goto err_finalize;
>   
>   err_finalize:
> +	drm_pagemap_migrate_unmap_pages(devmem_allocation->dev, pagemap_addr, dst, npages,
> +					DMA_FROM_DEVICE, &state);
>   	if (err)
>   		drm_pagemap_migration_unlock_put_pages(npages, dst);
>   	migrate_device_pages(src, dst, npages);
>   	migrate_device_finalize(src, dst, npages);
> -	drm_pagemap_migrate_unmap_pages(devmem_allocation->dev, pagemap_addr, dst, npages,
> -					DMA_FROM_DEVICE, &state);
>   
>   err_free:
>   	kvfree(buf);
> @@ -1305,14 +1305,14 @@ static int __drm_pagemap_migrate_to_ram(struct vm_area_struct *vas,
>   		goto err_finalize;
>   
>   err_finalize:
> -	if (err)
> -		drm_pagemap_migration_unlock_put_pages(npages, migrate.dst);
> -	migrate_vma_pages(&migrate);
> -	migrate_vma_finalize(&migrate);
>   	if (dev)
>   		drm_pagemap_migrate_unmap_pages(dev, pagemap_addr, migrate.dst,
>   						npages, DMA_FROM_DEVICE,
>   						&state);
> +	if (err)
> +		drm_pagemap_migration_unlock_put_pages(npages, migrate.dst);
> +	migrate_vma_pages(&migrate);
> +	migrate_vma_finalize(&migrate);

LGTM
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>

>   err_free:
>   	kvfree(buf);
>   err_out: