Re: [PATCH v2] drm/pagemap: Clear driver-provided PFNs from migration PFN array

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

On 22-07-2026 02:13, Matthew Brost wrote:
> DRM pagemap overloads the migration PFN array to store driver-provided
> PFNs before calling migrate_vma_*() to finalize the migration. If an
> error occurs during the incremental copy phase, the migration PFN
> entries are reverted to their original state. After reverting the
> device-folio mutations, clear any remaining driver-provided PFNs to
> avoid confusing the migrate_vma_*() helpers.
> 
> Also clear any driver-provided PFNs if populate_devmem_pfn() fails, as
> a precaution against stale entries being interpreted as migration PFNs.
> 
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Fixes: 3902846af36b ("drm/pagemap Fix error paths in drm_pagemap_migrate_to_devmem")
> Fixes: ec265e1f1cfc ("drm/pagemap: Support source migration over interconnect")
> Cc: stable@vger.kernel.org
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>

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

> 
> ---
> v2:
>   - Be paranoid and also clear driver-provided on populate_devmem_pfn()
>     failure (Sashiko)
> ---
>   drivers/gpu/drm/drm_pagemap.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
> index 15c78eca180b..892b325fa99b 100644
> --- a/drivers/gpu/drm/drm_pagemap.c
> +++ b/drivers/gpu/drm/drm_pagemap.c
> @@ -727,8 +727,10 @@ int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem *devmem_allocation,
>   	}
>   
>   	err = ops->populate_devmem_pfn(devmem_allocation, npages, migrate.dst);
> -	if (err)
> -		goto err_aborted_migration;
> +	if (err) {
> +		npages = 0;
> +		goto err_finalize;
> +	}
>   
>   	own_pages = 0;
>   
> @@ -807,8 +809,11 @@ int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem *devmem_allocation,
>   		msecs_to_jiffies(mdetails->timeslice_ms);
>   
>   err_finalize:
> -	if (err)
> +	if (err) {
>   		drm_pagemap_migration_unlock_put_pages(npages, migrate.dst);
> +		for (i = npages; i < npages_in_range(start, end); ++i)
> +			migrate.dst[i] = 0;
> +	}
>   err_aborted_migration:
>   	migrate_vma_pages(&migrate);
>