From: Ralph Campbell <rcampbell@xxxxxxxxxx> Use of pte_write(pte) is only valid for present pte, the common code which set the migration entry can be reach for both valid present pte and special swap entry (for device memory). Fix the code to use the mpfn value which properly handle both cases. On x86 this did not have any bad side effect because pte write bit is below PAGE_BIT_GLOBAL and thus special swap entry have it set to 0 which in turn means we were always creating read only special migration entry. So once migration did finish we always write protected the CPU page table entry (moreover this is only an issue when migrating from device memory to system memory). End effect is that CPU write access would fault again and restore write permission. Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx> Signed-off-by: Jérôme Glisse <jglisse@xxxxxxxxxx> --- mm/migrate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/migrate.c b/mm/migrate.c index 5d0dc7b85f90..a5c559d8e0e7 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2269,7 +2269,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, ptep_get_and_clear(mm, addr, ptep); /* Setup special migration page table entry */ - entry = make_migration_entry(page, pte_write(pte)); + entry = make_migration_entry(page, mpfn & + MIGRATE_PFN_WRITE); swp_pte = swp_entry_to_pte(entry); if (pte_soft_dirty(pte)) swp_pte = pte_swp_mksoft_dirty(swp_pte); -- 2.14.3
