On Mon, Jan 05, 2026 at 12:18:27PM +0100, Francois Dugast wrote:
> This code was written by Matt Brost. This is a placeholder until his
> patch is available.
>
> Cc: Matthew Brost <[email protected]>
> Signed-off-by: Francois Dugast <[email protected]>
> ---
> drivers/gpu/drm/drm_pagemap.c | 36 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
> index db3795f03aca..05e708730132 100644
> --- a/drivers/gpu/drm/drm_pagemap.c
> +++ b/drivers/gpu/drm/drm_pagemap.c
> @@ -452,6 +452,39 @@ static int drm_pagemap_migrate_range(struct
> drm_pagemap_devmem *devmem,
> return ret;
> }
>
> +/**
> + * drm_pagemap_cpages() - Count collected pages
> + * @migrate_pfn: Array of migrate_pfn entries to account
> + * @npages: Number of entries in @migrate_pfn
> + *
> + * Compute the total number of minimum-sized pages represented by the
> + * collected entries in @migrate_pfn. The total is derived from the
> + * order encoded in each entry.
> + *
> + * Return: Total number of minimum-sized pages.
> + */
> +static int drm_pagemap_cpages(unsigned long *migrate_pfn, unsigned long
> npages)
> +{
> + unsigned long i, cpages = 0;
> +
> + for (i = 0; i < npages;) {
> + struct page *page = migrate_pfn_to_page(migrate_pfn[i]);
> + struct folio *folio;
> + unsigned int order = 0;
> +
> + if (!page)
> + goto next;
Actually I think on a NULL page we can check compond bit in the mpfn set
and increment by 512 too.
Matt
> +
> + folio = page_folio(page);
> + order = folio_order(folio);
> + cpages += NR_PAGES(order);
> +next:
> + i += NR_PAGES(order);
> + }
> +
> + return cpages;
> +}
> +
> /**
> * drm_pagemap_migrate_to_devmem() - Migrate a struct mm_struct range to
> device memory
> * @devmem_allocation: The device memory allocation to migrate to.
> @@ -554,7 +587,8 @@ int drm_pagemap_migrate_to_devmem(struct
> drm_pagemap_devmem *devmem_allocation,
> goto err_free;
> }
>
> - if (migrate.cpages != npages) {
> + if (migrate.cpages != npages &&
> + drm_pagemap_cpages(migrate.src, npages) != npages) {
> /*
> * Some pages to migrate. But we want to migrate all or
> * nothing. Raced or unknown device pages.
> --
> 2.43.0
>
