Commit 139ab31a authored by Matthew Brost's avatar Matthew Brost
Browse files

drm/pagemap: Correct cpages calculation for migrate_vma_setup 



cpages returned from migrate_vma_setup represents the total number of
individual pages found, not the number of 4K pages. The math in
drm_pagemap_migrate_to_devmem for npages is based on the number of 4K
pages, so cpages != npages can fail even if the entire memory range is
found in migrate_vma_setup (e.g., when a single 2M page is found).
Add drm_pagemap_cpages, which converts cpages to the number of 4K pages
found.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: linux-mm@kvack.org
Reviewed-by: default avatarFrancois Dugast <francois.dugast@intel.com>
Signed-off-by: default avatarFrancois Dugast <francois.dugast@intel.com>
Reviewed-by: default avatarBalbir Singh <balbirs@nvidia.com>
Signed-off-by: default avatarMatthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260312192126.2024853-4-francois.dugast@intel.com
parent 2e03c0c5

drivers/gpu/drm/drm_pagemap.c

+37 −1
Original line number Diff line number Diff line
@@ -452,6 +452,41 @@ 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) {

			folio = page_folio(page);

			order = folio_order(folio);

			cpages += NR_PAGES(order);

		} else if (migrate_pfn[i] & MIGRATE_PFN_COMPOUND) {

			order = HPAGE_PMD_ORDER;

			cpages += NR_PAGES(order);

		}



		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 +589,8 @@ 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.