The patch titled
Subject: mm/migrate: properly preserve write attribute in special migrate entry
has been added to the -mm tree. Its filename is
mm-migrate-properly-preserve-write-attribute-in-special-migrate-entry.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-migrate-properly-preserve-write-attribute-in-special-migrate-entry.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-migrate-properly-preserve-write-attribute-in-special-migrate-entry.patch
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------------------------------------------------------
From: Ralph Campbell <rcampbell@xxxxxxxxxx>
Subject: mm/migrate: properly preserve write attribute in special migrate entry
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.
Link: http://lkml.kernel.org/r/20180402023506.12180-1-jglisse@xxxxxxxxxx
Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Signed-off-by: Jérôme Glisse <jglisse@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff -puN mm/migrate.c~mm-migrate-properly-preserve-write-attribute-in-special-migrate-entry mm/migrate.c
--- a/mm/migrate.c~mm-migrate-properly-preserve-write-attribute-in-special-migrate-entry
+++ a/mm/migrate.c
@@ -2346,7 +2346,8 @@ again:
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);
_
Patches currently in -mm which might be from rcampbell@xxxxxxxxxx are
mm-hmm-documentation-editorial-update-to-hmm-documentation.patch
mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v3.patch
mm-hmm-use-device-driver-encoding-for-hmm-pfn-v2-fix.patch
mm-hmm-use-device-driver-encoding-for-hmm-pfn-v2-fix-2.patch
mm-migrate-properly-preserve-write-attribute-in-special-migrate-entry.patch
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