linux-ext4 - RE: [PATCH v1 04/15] mm: add device coherent checker to remove migration pte

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Date:   Thu, 5 May 2022 21:38:07 +0000
From:   "Sierra Guiza, Alejandro (Alex)" <Alex.Sierra@....com>
To:     "Sierra Guiza, Alejandro (Alex)" <Alex.Sierra@....com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "apopple@...dia.com" <apopple@...dia.com>
CC:     "rcampbell@...dia.com" <rcampbell@...dia.com>,
        "willy@...radead.org" <willy@...radead.org>,
        "david@...hat.com" <david@...hat.com>,
        "Kuehling, Felix" <Felix.Kuehling@....com>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "jglisse@...hat.com" <jglisse@...hat.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "hch@....de" <hch@....de>
Subject: RE: [PATCH v1 04/15] mm: add device coherent checker to remove
 migration pte

@apopple@...dia.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@...ts.freedesktop.org> On Behalf Of Alex
> Sierra
> Sent: Thursday, May 5, 2022 4:34 PM
> To: jgg@...dia.com
> Cc: rcampbell@...dia.com; willy@...radead.org; david@...hat.com;
> Kuehling, Felix <Felix.Kuehling@....com>; apopple@...dia.com; amd-
> gfx@...ts.freedesktop.org; linux-xfs@...r.kernel.org; linux-mm@...ck.org;
> jglisse@...hat.com; dri-devel@...ts.freedesktop.org; akpm@...ux-
> foundation.org; linux-ext4@...r.kernel.org; hch@....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@....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