RE: [PATCH v1 04/15] mm: add device coherent checker to remove migration pte

Sierra Guiza, Alejandro (Alex)
2022-05-05T21:38:24Z

@apopple@nvidia.com Could you please check this patch? It's somehow related to migrate_device_page() for long term device coherent pages.

Regards,
Alex Sierra
> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> On Behalf Of Alex
> Sierra
> Sent: Thursday, May 5, 2022 4:34 PM
> To: jgg@nvidia.com
> Cc: rcampbell@nvidia.com; willy@infradead.org; david@redhat.com;
> Kuehling, Felix <Felix.Kuehling@amd.com>; apopple@nvidia.com; amd-
> gfx@lists.freedesktop.org; linux-xfs@vger.kernel.org; linux-mm@kvack.org;
> jglisse@redhat.com; dri-devel@lists.freedesktop.org; akpm@linux-
> foundation.org; linux-ext4@vger.kernel.org; hch@lst.de
> Subject: [PATCH v1 04/15] mm: add device coherent checker to remove
> migration pte
>
> During remove_migration_pte(), entries for device coherent type pages that
> were not created through special migration ptes, ignore _PAGE_RW flag. This
> path can be found at migrate_device_page(), where valid vma is not
> required. In this case, migrate_vma_collect_pmd() is not called and special
> migration ptes are not set.
>
> Signed-off-by: Alex Sierra <alex.sierra@amd.com>
> ---
> mm/migrate.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c index
> 6c31ee1e1c9b..e18ddee56f37 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -206,7 +206,8 @@ static bool remove_migration_pte(struct folio *folio,
> * Recheck VMA as permissions can change since migration
> started
> */
> entry = pte_to_swp_entry(*pvmw.pte);
> - if (is_writable_migration_entry(entry))
> + if (is_writable_migration_entry(entry) ||
> + is_device_coherent_page(pfn_to_page(pvmw.pfn)))
> pte = maybe_mkwrite(pte, vma);
> else if (pte_swp_uffd_wp(*pvmw.pte))
> pte = pte_mkuffd_wp(pte);
> --
> 2.32.0